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What is Hard Drive?Hard disk, hard disk drive (HDD), hard disk, or fixed disk is the most important storage device of computer. It is composed of one or more aluminum or glass discs. These discs are covered with ferromagnetic material. Your documents, pictures, music, videos, programs, application preferences, and operating system represent digital content all can be stored on a hard drive. Most hard drives are permanently sealed and fixed in the hard drive. Early hard disk storage media was replaceable, but today's hard disk is a fixed storage medium, which is sealed in a case. With the development, removable hard disks have also appeared, and they are becoming more and more popular with different types. In addition, most of the hard disks installed on microcomputers are called Winchester hard drive.Hard DriveTopics Covered in this GuideWhat is Hard Drive?Hard Drive Tech ParametersHard Drive ClassificationsHard Disk StructureHow Does Hard Disk Work?Hard Drive MaintenanceUsing TipsHard Drive FaultsTypes of Hard Disk InterfacesCan a Computer Run without a Hard Drive?Should I Buy SSD or HDD?What the Defferences between HDD and SSD?What is the Lifespan of a Hard Drive?How Much Do Hard Drives Cost?What are the Best Hard Drives?Hard Drive Tech Parameters1) HD CapacityCapacity is the most important parameter of the hard disk. The capacity of the hard disk is measured in megabytes (MB) or gigabytes (GB). However, the hard disk manufacturer usually takes 1G=1000MB in the nominal hard disk capacity, so the capacity we see in the BIOS or when formatting the hard disk will be smaller than the manufacturer’s nominal value.The hard disk capacity index also includes the single-disk capacity. It refers to the capacity of a single disk of a hard disk. The larger the single disk capacity, the lower the unit cost and the shorter the average access time. For users, the capacity of the hard disk is like the computer memory, and it will never be too much.2) Rotational SpeedRotational speed, or spindle speed is the rotation speed of the motor spindle in the hard disk, which is the maximum number of revolutions that the hard disk platter can complete in one minute. It is one of the important parameters indicating the grade of the hard disk. It is one of the key factors that determine the internal transmission rate of the hard disk, and directly affects the speed of the hard disk to a large extent. The faster the rotation speed of the hard disk, the faster the hard disk can find files. The hard disk speed is expressed in revolutions per minute, and the unit is expressed as RPM(revolutions per minute). The larger the RPM value, the faster the internal transfer rate, the shorter the access time, and the better the overall performance of the hard drive.The spindle motor of the HDD makes the platters to rotate at a high speed, generating buoyancy to make the head float above the platters. Bring the sector of the data to be accessed below the head, the faster the speed, the shorter the waiting time. Therefore, the rotational speed largely determines the read speed of the hard disk.The rotation speed of ordinary hard disks for household use is generally 5400rpm and 7200rpm. High-speed hard disks are the first choice for desktop users. For notebook users, it is mainly 4200rpm and 5400rpm. Although some companies have released 7200rpm notebook hard disks, they are still rare in the market. Users have the highest requirements on server for hard disk performance. The speed of SCSI hard disks used in servers is basically 10000rpm, and even 15000rpm. The performance is much higher than that of household products.A higher speed can shorten the average seek time and actual read and write time of the hard disk. However, as the speed of the hard disk continues to increase, it also brings negative effects such as temperature rise, heavy motor spindle wear, and great operating noise. The speed of notebook hard disks is lower than that of desktop hard disks, which is affected to a certain extent by this factor. The internal space of the notebook is small, and the size of the notebook hard disk (2.5 inches) is also designed to be smaller than that of the desktop hard disk (3.5 inches). The temperature rise caused by the increase in speed puts higher requirements on the heat dissipation performance of the notebook itself. In addition, the noise becomes larger, it is necessary to take noise reduction measures, so more technique requirements on the notebook hard disk productions. At the same time, the increase in speed, while the others remain unchanged, means that the power consumption of the motor will increase, the more electricity is consumed per unit time, and the working time of the battery is shortened, so that the portability of the notebook will be affected. Therefore, notebook hard drives generally use a relatively low-speed 4200rpm hard drive.3) Access TimeThe average access time refers to the time required for the head to reach the target track position from the starting position and find the data sector to be read and written on the target track.The average access time reflects the read and write speed of the hard disk, which includes the seek time and waiting time of the hard disk, that is, average access time = average seek time + average waiting time.The average seek time of the hard disk refers to the time required for the head of the hard disk to move to the specified track on the disk surface. This time is of course as small as possible. The average seek time is usually between 8ms and 12ms, while a SCSI HDD should be less than or equal to 8ms.The waiting time of the hard disk, also known as the Latency, refers to the time that the magnetic head is already in the track to be accessed and waiting for the sector to be accessed to rotate below the head. The average waiting time is half of the time required for the disc to rotate one round, and should generally be less than 4ms.4) Data Transfer RateData transfer rate refers to the speed at which the hard disk reads and writes data, in megabytes per second (MB/s). It includes internal data transfer rate and external data transfer rate.The internal transfer rate is also known as the sustained transfer rate, which reflects the performance of the hard disk buffer when it is not in use. The internal transfer rate mainly depends on the rotation speed of the hard disk.The external transfer rate is also called the burst data transfer rate or the interface transfer rate. It is nominally the data transfer rate between the system bus and the hard disk buffer. The type of hard disk interface is related to the size of the hard disk cache.The maximum external transfer rate of the Fast ATA interface HD is 16.6MB/s, while the Ultra ATA interface hard disk reaches 33.3MB/s.The hard disk using SATA (Serial ATA) port is also called serial hard disk. Serial ATA adopts a serial connection method. The serial ATA bus uses an embedded clock signal and has a stronger error correction capability. Compared with the past, its biggest difference is that it can check the transmission instructions (not just data). Errors are found to be automatically corrected, which greatly improves the reliability of data transmission. The serial interface also has the advantages of simple structure and support for hot swapping.5) Cache MemoryCache memory is a memory chip on the hard disk controller with extremely fast access speed. It is a buffer between the internal storage of the hard disk and the external interface. Since the internal data transfer speed of the hard disk is different from the transfer speed of the external interface, the cache plays a role as a buffer among them. The size and speed of the cache is an important factor directly related to the transmission speed of the hard disk, which can greatly improve the overall performance of the hard disk. When the hard disk accesses fragmented data, data needs to be continuously exchanged between the hard disk and the memory. With a large cache, the fragmented data can be temporarily stored in the cache, reducing the load on the external system and improving the data transmission speed. Hard Drive Classifications1) Mechanical Hard Disk (HDD)HDDMechanical hard disk (HDD) is a traditional hard disk, one of the main storage media for computers. It is composed of one or more magnetic discs made of aluminum or glass, magnetic heads, rotating shafts, control motors, head controllers, data converters, interfaces and caches. When working, the head is suspended on a high-speed rotating disc to read and write data. Mechanical hard disk is a computer storage device that integrates precision machinery, microelectronic circuits, and electromagnetic conversion.2) Solid State Drive (SSD)SSDA solid state drive (SSD) is an array storage composed of multiple flash memory chips plus a main control and cache, and belongs to a hard drive made of an array of solid electronic storage chips. Compared with a mechanical hard disk, the read speed is faster and the seek time is shorter, which can speed up the operating system startup speed and the software startup speed.3) Solid State Hybrid Drive (SSHD)SSHDSolid state hybrid drive is a combination of mechanical hard disk and solid-state hard disk. It uses small-capacity flash memory particles to store commonly used files. Disk is the most important storage medium. Flash memory only serves as a buffer to reduce seek time and improve efficiency. Hard Disk StructureThe hard disk is one of the most important storage for computers. Most of the software needed for the computer to function properly is stored on the hard drive. Because the storage capacity of hard disk is large, it is different from computer memory and optical disk. Hard disks are storage devices based on hard rotating disks used on computers. It stores and retrieves digital data on a flat magnetic surface.Take a Look Inside a Hard Drive1) Magnetoresistive Heads (MR heads)The magnetoresistive head is the most expensive part of the hard disk, and it is also the most important and critical part of the HD technology. The traditional magnetic head is an electromagnetic induction magnetic head that combines reading and writing. However, the reading and writing of hard disks are two completely different operations to limit the hard disk design. The MR head uses a separate head structure: the write head still uses the traditional magnetic induction head (MR head cannot write), and the read head uses a new type of MR head. In this way, during the design, the different characteristics of the two can be optimized separately to obtain the best read/write performance. In addition, the MR head gets the signal amplitude through changes in resistance rather than changes in current, so it is very sensitive to signal changes, and the accuracy of reading data is correspondingly improved. Further more, because the read signal amplitude has nothing to do with the track width, the HD track can be made very narrow, thereby increasing the density of the disc. In addition, GMR heads (Giant Magnetoresistive heads) made of materials with a multi-layer structure and better magnetoresistive effect have gradually become popular.2) Magnetic TrackWhen the disk rotates, if the head is held in one position, each head will draw a circular track on the surface of the disk, called tracks. They are invisible to the naked eye at all, because they are only some magnetized areas on the disk surface that are magnetized in a special way, and the information on the disk is stored along such tracks. Adjacent tracks are not close to each other. This is because when the magnetization units are too close, the magnetism will affect each other, and at the same time it will also cause difficulties for the magnetic head to read and write. For example, a 1.44MB 3.5-inch floppy disk has 80 tracks on one side, and the track density on the hard disk is much greater than this value, usually there are thousands of tracks on one side.The surface of the disk is coated with a magnetic medium used for recording, which are magnetic particles under the microscope. The polarity of tiny magnetic particles can be quickly changed by the magnetic head, and can be maintained stably after the change. The system distinguishes 0 or 1 in the binary system through changes in magnetic flux and magnetoresistance. It is precisely because all operations are performed under microscopic conditions, so if the hard disk is operated at high speed while being shocked by external forces, it may cause irreversible data loss due to the head slaps on the surface of the disk. In addition, the uniaxial anisotropy and volume of the magnetic particles will obviously affect the thermal stability of the magnetic particles, and the thermal stability determines the stability of the magnetic particle, that is, the correctness and stability of the stored data. However, it cannot be increased blindly, because it is limited by the write field that the magnetic head can provide and the signal-to-noise ratio of the medium.3) FanEach track on the disk is equally divided into several arc segments, which are the sectors of the disk. Each sector can store 512 bytes of info. The hard disk drive reads and writes data to the disk  from the sectors. 4) CylinderA hard disk is usually composed of a set of overlapping disks. Each disk surface is divided into an equal number of tracks, and numbered from the "0" on the outer edge. The tracks with the same number form a cylinder. The number of cylinders on a disk is equal to the number of tracks on a disk. Since each disk surface has its own head, the number of disk surfaces is equal to the total number of heads. The so-called CHS of the hard disk, namely Cylinder, Head, Sector. So when the number of CHS of the hard disk is known, the capacity of the hard disk can be determined. The capacity of the hard disk is the number of cylinders and the number of sectors. How Does Hard Disk Work?How Do Hard Drives Work?When the hard disk is working, never turn off the power forcibly, which will cause physical damage to the hard disk and data loss. In addition, with high-speed components in the hard disk, if the high-speed disk is shut down forcibly and suddenly, which is more likely to cause damage to the hard disk. So don't turn on the computer immediately after shutting down. This requires time buffering.When the hard disk is working, try to avoid its vibration, because the distance between the magnetic head and the magnetic disk is very close. If it is subjected to severe vibration, the magnetic head will hit the magnetic disk to damage it, which will make the entire hard drive unusable.In the process of using the hard disk, many users compress files to reduce the use of disk space. This will cause the compressed volume file to continue to grow. The data access speed also slowed down, and the number of reads and writes increased, which would affect the heat generation and stability of the hard disk, even reduce service life.  Hard Drive MaintenanceFirst of all, the impact of dust on the hard disk is not small. If dust is attracted to the circuit board, it will cause unstable operation of the hard disk or damage to internal parts. The functional working status of the hard disk has a great relationship with the temperature. Too high or too low temperature will cause the clock frequency of the crystal oscillator to change, which will cause the circuit components to malfunction. In addition, if the temperature is too low, it will cause the air moisture condenses on the component, causing a short circuit.Second, we need to clear your hard drive regularly. This will increase the speed of your hard drive. If there are too many junk files on the hard disk, the speed will slow down and the tracks may be damaged. However, clean up frequently will also reduce the service life of the hard drive.Finally, it is anti-virus. Viruses are the biggest threat to the files stored on the hard drive. Therefore, once we found that the virus should be cleared up in time and try not to format the hard disk. Using Tips1) Don't shut down suddenly while working.When the hard disk starts to work, it is generally in high-speed rotation, if we suddenly turn off the power in the middle, it may cause violent friction between the head and the platter to damage the hard disk. Therefore, it is necessary to avoid this. When shutting down, you must pay attention to whether the hard disk indicator on the panel is still flashing, only the indicator stops flashing and then hard disk read and write ends, you can turn off the computer.2) Prevent dust from entering.Dust can cause great damage to the hard disk. This is because in a severely dusty environment, the hard disk can easily attract dust particles in the air, causing them to accumulate on the internal circuit components of the hard disk for a long time, which will affect the heat of the electronic components, causing the temperature of the circuit components to rise, and resulting in leakage or burnout of the components.In addition, dust may also absorb moisture, corrode the electronic circuits inside the hard disk, and cause some invisible problems. Therefore, although the volume of dust is small, the harm to the hard disk cannot be underestimated. Therefore, it is necessary to maintain environmental sanitation and reduce the humidity and dust content in the air. In addition, users cannot remove the hard disk cover by themselves, otherwise the dust in the air will enter the hard disk and scratch the platters or heads during read and write operations.3) Temperature ControlAs we all known, temperature affects the service life of the hard disk. A certain amount of heat is generated when the hard disk is working, so there is a heat dissipation problem during use. 20～25℃ is better. Temperature can also cause failure of hard disk circuit components, and magnetic media can also cause recording errors due to thermal expansion.On one hand, when the humidity is too high, the surface of the electronic components may absorb a layer of water, oxidizing and corroding the electronic circuits, resulting in poor contact or even short circuits, and it will also cause the magnetic force of the magnetic medium to change, causing data reading and writing errors. On the other hand, it is easy to accumulate a large amount of static charge generated by the rotation of the machine in low temperature, which will burn out the CMOS circuit, attract dust and damage the head and scratch the disk. In addition, try not to make the hard disk close to strong magnetic fields, such as loud speakers, motors, radios, mobile phones, etc., so as to prevent the data recorded on the hard disk from being damaged due to magnetization.Hard Disk Drive StructureHard Drive Faults1) HD Cooling FanConsidering the heat dissipation effect, many people install hard drive cooling fans for their computer hard drives. However, some low-end fans have obvious vibrations and can transmit vibration to the hard drive. In the long term, it will definitely affect the life of the hard drive.2) Optical DriveThe reading speed of mainstream optical drives has reached more than 50 times speed. When the optical disc rotates at a high speed, the vibration of the optical drive itself will drive the resonance of the chassis, which affects the work of the hard disk. And this kind of high-speed rotation generates a lot of heat, because the optical drive is so close to the hard drive, the heat released from the optical drive will surely increase the temperature of the hard drive.3) Static ElectricityIn the process of repairing the computer, many people hold the hard disk with their hands, but in dry weather, tens of thousands of volts of static electricity may accumulate on the hands of people, which may break down the chips on the circuit board, causing the hard disk to malfunction.4) FormattingIf the computer hard disk has bad sectors, many users will take formatting measures. In fact, low format damages the hard disk greatly. It may cause the proliferation of bad sectors on the disk, and even cause the loss of hard disk parameters, making the hard disk unable to use.5) Power SupplyA low-quality computer will cause the hard drive to be disturbed by voltage fluctuations, especially when the hard drive is reading and writing. If there is a problem with the power supply, a hard drive can be scrapped in an instant.6) Magnetic FieldBecause the hard disk is a device that relies on magnetic media to record data, if it is interfered by the magnetic field of the external environment, it is likely to cause the loss of disk data, so you should try to stay away from the magnetic field environment. Types of Hard Disk InterfacesThere are five categories of hard disk interfaces: IDE, SATA, SCSI, SAS, FC1) IDE (Integrated Drive Electronics)IDE refers to the hard disk drive that integrates the controller and the disk body, and is a hard disk transmission interface. There is another name called ATA (advanced technology attachment).2) SATA (Serial ATA)SATA hard disk is called serial hard disk based on its serial data transmission method. In the process of data transmission, the data line and the signal line are used independently, and the transmission clock frequency remains independent. Therefore, compared with the previous PATA, the transmission rate of SATA can reach 30 times that of parallel. It can be said that SATA technology is not an improvement of PATA technology in a simple sense, but a new bus architecture.3) SCSI (Small Computer System Interface)SCSI invention is mainly because the hard disk speed of the original IDE interface is too slow. In fact, SCSI is not designed specifically for hard drives, in fact it is a bus-type interface, working independently of the system bus.4) SAS (Serial Attached SCSI)SAS is serial attached SCSI, which is a new generation of SCSI technology. Like the popular SATA hard disks, it uses serial technology to achieve higher transmission speeds, and improves internal space by shortening the cable. It is a brand new interface developed after the parallel SCSI interface, which is designed to improve the performance, availability, and expandability of the storage system, and provide compatibility with SATA hard drives.SAS interface tech can be backward compatible with SATA. Specifically, the compatibility of the two is mainly reflected in the compatibility of the physical layer and the protocol layer.5) FC (Fibre Channel)Just like the SCIS interface, FC is not an interface technology designed and developed for hard disks at first. It is specially designed for network systems. However, as storage systems require high speed, they are gradually applied to hard disk systems. FC hard disk was developed to improve the speed and flexibility of multi-disk storage system. Its appearance greatly improves the communication speed of multi-disk system, and it uses optical cable connections between systems in a point-to-point (or switching) configuration. There are something to note: the hard disk itself does not have an FC interface, where the cabinet has, which is interconnected with an optical fiber switch. Note: Get more info from Types of Hard Disk Drive Interface.Can a Computer Run without a Hard Drive?A computer can still function without a hard drive. This can be done through a network, USB, CD, or DVD. Computers can be booted over a network, through a USB drive, or even off of a CD or DVD. When you attempt to run a computer without a hard drive, you will often be asked for a boot device. Should I Buy SSD or HDD?1) According to data read and write speedA computer with the same configuration can reach a read and write speed of about 500M/S with a solid state drive, but about 150MB/S with a mechanical hard drive. The difference is nearly three times the speed, which makes the difference in computer response speed even greater.2) According to data security and shock resistanceSince the mechanical hard disk reads and writes data through the magnetic head to read the disk, it is easy to cause data damage due to the collision of the disk and the magnetic head during high-speed rotation, especially it is in the handling process that the disc may be damaged, so everyone needs to be extremely careful when touching it.3) According to weight and volumeCompared with mechanical hard disks, solid state drives are smaller and lighter in appearance, and has stronger performance and faster transfer speed than mechanical hard drives.4) According to noise and heat dissipationSince the solid state drive is made of flash memory particles, it is not equipped with mechanical parts and flash memory chips, and there is no disk and head mechanical motors, fans, etc., so that it can ensure absolute silence. The heat is also very small, and the heat dissipation is also very fast.5) According to power consumptionSSDs commonly use less power and result in longer battery life because data access is much faster and the device is idle more often. With their spinning disks, HDDs require more power when they start up than SSDs. For example, the general full-speed power consumption of a 3.5-inch mechanical hard disk is about 12W, and a 2.5-inch hard disk is only about 5W. The full-speed power consumption of the solid-state drive is about 10W, its working power is generally 2-3W, less than 1W in standby mode.Although solid state drives are definitely faster than mechanical hard drives from above mentioned, but it doesn’t mean that solid state drives are necessarily better than mechanical hard drives, because in terms of price and capacity, mechanical hard drives are "T" is the unit, and most of the solid-state drives are still in G. Although there are also "T", the price is beyond everyone's expectations. One more thing to note is that it is more difficult to restore data if the solid state drive is damaged, while the mechanical hard drive can restore data through repair. Therefore, in terms of data security, mechanical hard drives have more advantages in storing important data. In short, consider comprehensively according to the actual situations. What the Defferences between HDD and SSD?A hard disk drive (HDD) is a traditional storage device that uses mechanical platters and a moving read/write head to access data. A solid state drive (SSD) is a newer, faster type of device that stores data on instantly-accessible memory chips.Generally, SSDs are more durable than HDDs in extreme and harsh environments because they don't have moving parts such as actuator arms. SSDs can withstand accidental drops and other shocks, vibration, extreme temperatures, and magnetic fields better than HDDs.SSDs commonly use less power and result in longer battery life because data access is much faster and the device is idle more often. With their spinning disks, HDDs require more power when they start up than SSDs. However, when not in use, magnetic drives are more reliable for long-term storage than flash memory ones. Thus, HDDs are more capable of long time storage than SSDs when powered off.While normal HDDs can last about 10 years max in reality, and an SSD lifespan has a built-in time of death. To keep it simple: an electric effect results in the fact that data can only be written on a storage cell inside the chips between approximately 3,000 and 100,000 times during its lifetime.As for price, SSDs are more expensive than hard drives in terms of dollar per gigabyte. A 1TB internal 2.5-inch hard drive costs between $40 and $60, but as of this writing, the very cheapest SSDs of the same capacity and form factor start at around $100.With their ruggedness and low energy consumption, SSDs are becoming more popular with portable PCs. With all the advantages that SSD has over HDD, price, availability and capacity are probably the primary factors constraining the acceptance of this new technology. Note: Get more info from SSD vs HDD: Is an SSD Really Necessary?What is the Lifespan of a Hard Drive?Though the average might be three to five years, hard drives can theoretically last much longer (or shorter, for that matter). If a hard drive works 24 hours continuously, it will be damaged in less than 3 years. After normal use, there should be no problem for 5 or 10 years. During use, the garbage must be cleaned regularly and kept HD cool, so as not to get stuck.As with most things, if you take care of your hard drive, it will better last to its potential. How Much Do Hard Drives Cost?A 1TB internal 2.5-inch hard drive costs between $40 and $60, but as of this writing, the very cheapest SSDs of the same capacity and form factor start at around $100. That translates into 4 to 6 cents per gigabyte for the hard drive versus 10 cents per gigabyte for the SSD.According to market trend, the number of hard drives sold each year has declined recently due to the migration of consumer PCs to SSDs, and also demand for higher-capacity HDDs by exascale datacenters. When demand for HDDs spikes, retailers sell out quickly, and prices increase as dealers come into play. What are the Best Hard Drives?Best Hard Drives at a Glance1️⃣Seagate BarraCuda2️⃣Toshiba X3003️⃣WD VelociRaptor4️⃣WD Blue Desktop5️⃣Seagate Firecuda Desktop6️⃣Seagate IronWolf NAS7️⃣Seagate FireCuda Mobile8️⃣WD My Book9️⃣G-Technology G-Drive

IntroductionFLASH is a type of non-volatile memory that retains data even when power is disconnected. Unlike RAM, which can rewrite data at the byte level, flash memory operates differently. A flash memory chip consists of an array of data storage cells organized into blocks, with each block containing multiple pages (typically 64 to 256 pages in modern devices, though older devices used 32 pages). A page is usually 2KB, 4KB, 8KB, or 16KB in modern NAND flash, though the original specification was 512 bytes plus spare area, as flash was initially developed as a disk replacement technology.What Is Flash Memory?Ⅰ Types of Flash MemoryFlash memory is widely used as a storage medium in digital cameras, smartphones, tablets, USB drives, SSDs, and various consumer electronics. Flash memory cards come in various form factors depending on manufacturers and applications, including USB flash drives, CompactFlash (CF card), MultiMediaCard (MMC card), Secure Digital (SD card, microSD), Memory Stick, and XD-Picture Card (XD card). Note that SmartMedia (SM card) and Microdrive have been discontinued. While these flash cards have different physical formats and specifications, their underlying technical principles remain similar.Flash memory includes two main architectural types: NOR Flash and NAND Flash. NOR Flash is a random access device with dedicated address and data lines (similar to SRAM), allowing byte-level read and write operations and direct access to any memory location, making it an excellent ROM alternative, such as in computer BIOS chips. NAND Flash, however, lacks dedicated address lines and cannot be directly addressed. It is controlled by sending commands and addresses through an I/O interface, meaning NAND Flash can only be accessed in pages, making it more suitable for sequential data storage.Ⅱ NAND Flash MemoryNAND Flash is extensively used in high-capacity storage devices such as memory cards, USB drives, SSDs, eMMC, and UFS storage. NAND Flash cells are categorized by the number of bits stored per cell: SLC (Single-Level Cell), MLC (Multi-Level Cell), TLC (Triple-Level Cell), and QLC (Quad-Level Cell). SLC stores 1 bit per cell, MLC stores 2 bits, TLC stores 3 bits, and QLC stores 4 bits per cell.As more bits are stored in a single cell, the read/write performance decreases, endurance diminishes, but cost per gigabyte is reduced, making higher-density options more economical for consumer applications.ItemsSLCMLCTLCQLCBits Per Cell1234P/E Cycles50,000-100,0003,000-10,0001,000-3,000100-1,000Read Time (μs)255075100Program Time (μs)200-300600-900900-13501350-2000Erase Time (ms)1.5-234.56-8SLC is primarily used in enterprise, industrial, and military applications due to its high-speed writing, low error rate, and exceptional durability.MLC is targeted at consumer and prosumer applications, offering twice the capacity of SLC at lower cost. It's suitable for USB drives, smartphones, digital cameras, and consumer-grade SSDs.TLC has become the mainstream choice for consumer SSDs and SD cards due to its balance of cost, capacity, and acceptable performance for everyday use.QLC, introduced more recently, offers even higher density and lower cost per gigabyte, making it increasingly popular in budget SSDs and high-capacity storage solutions, though with reduced endurance.As a practical solid-state storage medium, NAND Flash has unique physical characteristics requiring specialized management. Designers face several key challenges:1) Erase-before-write requirement: Data cannot be overwritten directly; blocks must be erased before new data can be written2) Wear mechanism: Limited program/erase (P/E) cycles impose durability constraints3) Read/write interference: Operations can cause data errors in adjacent cells4) Data retention: Charge leakage over time can cause data loss5) Bad block management: Both factory defects and runtime failures must be managedKey technologies addressing these challenges include:1) Cell type selection: Choosing appropriate NAND type (SLC/MLC/TLC/QLC) based on application requirements2) Wear leveling algorithms: Distributing write operations evenly across all blocks to maximize lifespan3) Bad block management: Identifying and mapping out defective blocks to ensure data integrity4) Error Correction Code (ECC): Detecting and correcting bit errors using advanced algorithms like BCH or LDPC5) Write amplification mitigation: Minimizing unnecessary write operations to extend device life6) Garbage collection: Consolidating valid data and reclaiming space from partially used blocksData is stored as electrical charge in Flash memory cells. The amount of stored charge depends on the voltage applied to the Control Gate, which controls whether charge is injected or removed from the floating gate.1) For programming (writing) NAND Flash, voltage is applied to the Control Gate to inject electrons into the floating gate. When charge exceeds the threshold voltage (Vth), the cell represents a logical 0.2) For erasing NAND Flash, electrons are removed from the floating gate. When charge falls below the threshold voltage (Vth), the cell represents a logical 1. Ⅲ NOR Flash MemoryNOR Flash, similar to conventional memory, supports random access, enabling XIP (eXecute In Place) functionality. This allows code execution directly from the flash without copying to RAM, making it ideal for boot code, BIOS/UEFI firmware, and embedded system applications requiring immediate code execution.NOR Flash is categorized into two types based on host interface: Parallel NOR Flash and Serial NOR Flash.Parallel NOR Flash connects directly to the host controller with its contents mapped into the CPU address space, eliminating the need to copy to RAM. Early BIOS implementations used the FWH (Firmware Hub) interface, a parallel connection that has been largely obsoleted due to pin count and speed limitations.Serial NOR Flash is more cost-effective than Parallel NOR Flash and typically connects to the host processor or Platform Controller Hub (PCH) via SPI (Serial Peripheral Interface), Quad-SPI (QSPI), or Octal-SPI interfaces. Modern implementations support higher speeds through multi-lane configurations.Today, virtually all UEFI/BIOS firmware, embedded systems, IoT devices, and many consumer electronics use NOR Flash. Typical capacities range from 1MB to 256MB, with 16MB-128MB being common for modern UEFI implementations. While more expensive per gigabyte than NAND, NOR Flash offers superior reliability and random access performance.NOR Flash has slower erase speeds and lower erase cycle counts compared to NAND, but these limitations rarely impact BIOS/firmware performance or cause device failures due to the infrequent update nature of firmware. Ⅳ NAND Flash vs NOR FlashCompared with NOR flash memory, NAND flash memory requires fewer transistors per cell to store the same amount of data, resulting in smaller die size and higher storage density. This architectural difference makes NAND significantly more cost-effective for high-capacity storage applications.In terms of read speed, NOR flash memory offers faster random access than NAND flash memory, with typical access times of 50-100ns compared to NAND's page-based access. However, NAND flash memory significantly outperforms NOR in sequential write and erase operations. NAND's block-based erase operation is simpler and faster, erasing entire blocks (typically 128KB-4MB) at once.NOR flash memory requires all bits to be set to 1 during erase operations before programming. While NOR flash memory provides faster random access and simpler byte-level operations, its lower storage density and higher cost make it more suitable for code storage and execution. NAND flash memory provides extremely high cell density (modern single chips can exceed 1TB capacity), making it ideal for mass data storage with fast write and erase speeds. Additionally, NAND flash operates on page-based read/write units (typically 4KB-16KB) and block-based erase units, making it functionally similar to traditional disk drives.NAND Flash is more susceptible to bit errors than NOR Flash, necessitating robust Error Detection and Correction (EDC/ECC) algorithms. Modern NAND implementations use advanced ECC schemes like BCH (Bose-Chaudhuri-Hocquenghem) or LDPC (Low-Density Parity-Check) codes. Additionally, NAND Flash develops bad blocks over its lifetime. File systems like FAT on SD cards experience frequent rewrites of the file allocation table, and the P/E cycle count per block is critical to NAND Flash longevity. Balancing erase cycles across all blocks and managing bad blocks requires specialized firmware-level functionality including bad block management, wear leveling, ECC, and garbage collection. This management layer is called the FTL (Flash Translation Layer). Based on FTL implementation location, Flash Memory is categorized as Raw Flash or Managed Flash.Raw Flash requires the host system to implement FTL functionality, giving designers complete control but requiring significant software development. Managed Flash (such as eMMC, UFS, SD cards) includes an integrated controller that handles FTL operations transparently, simplifying host system design at the cost of reduced low-level control.Ⅴ Universal Flash Storage Versions ComparisonStorage performance significantly impacts device responsiveness and user experience. Universal Flash Storage (UFS) has become the dominant standard for high-performance mobile and embedded storage, replacing the older eMMC standard. UFS provides a standardized flash storage specification optimized for smartphones, tablets, automotive systems, and other performance-critical applications. Version numbers indicate generational improvements, with higher versions offering substantially better performance, features, and efficiency.✔️Version Comparison (Main Parameters)UFS Version1.01.12.02.13.03.14.0Introduced2011-02-242012-06-252013-09-182016-04-042018-01-302020-01-302023-09-14Bandwidth per lane300 MB/s600 MB/s1450 MB/s (HS-G3)2900 MB/s (HS-G4)5800 MB/s (HS-G5)Max. number of lanes12Max. total bandwidth300 MB/s1200 MB/s2900 MB/s (HS-G3)5800 MB/s (HS-G4)11600 MB/s (HS-G5)M-PHY version1.03.04.15.0UniPro version1.41.61.82.0✔️UFS 2.1 vs UFS 2.2The primary enhancement in UFS 2.2 over UFS 2.1 is the Write Booster feature, which significantly improves write performance. Write Booster uses SLC (Single-Level Cell) cache to accelerate write operations, providing faster application launches, improved browser cache loading, reduced video encoding times, and enhanced overall system responsiveness. This feature is particularly beneficial for burst write scenarios common in mobile devices.As eMMC has been phased out from mainstream consumer devices and NAND flash prices have decreased, UFS adoption has accelerated. UFS 2.2 briefly served as a transitional standard before UFS 3.x became mainstream in flagship devices.✔️UFS 3.0 vs UFS 3.1UFS 3.1 introduces three significant enhancements over UFS 3.0:1) Write Booster (Enhanced)Write Booster in UFS 3.1 is an enhanced version that increases device write speed substantially. This feature can boost write speeds up to 700 MB/s, compared to UFS 3.0's typical sequential write performance of around 500 MB/s. The mechanism works similarly to SLC caching in SSDs: a portion of TLC/QLC storage is dynamically configured to operate in SLC mode, providing faster write performance. Data is initially written to this high-performance buffer, then migrated to standard storage during idle periods, freeing the cache for subsequent operations.2) Deep Sleep ModeDeep Sleep enables the flash memory to enter an ultra-low-power state during extended idle periods, significantly reducing standby power consumption. This feature helps extend battery life during device standby and contributes to overall device thermal management. Deep Sleep can reduce idle power consumption by up to 40% compared to standard sleep modes.3) Host Performance Booster (HPB)HPB addresses long-term performance degradation by improving random read performance. As devices are used over time, file system fragmentation and the need to frequently reload the Logical-to-Physical (L2P) mapping table can cause performance degradation. HPB leverages the host device's RAM to cache portions of the L2P mapping table, reducing latency for random read operations. This is particularly effective at maintaining consistent performance after extended use, preventing the "slowdown over time" phenomenon common in storage devices. HPB can improve random read IOPS by up to 70% in fragmented scenarios.✔️UFS 4.0 - The Latest GenerationReleased in September 2023, UFS 4.0 represents the latest advancement in mobile storage technology. Key improvements include:• Doubled bandwidth: Up to 11.6 GB/s (5800 MB/s per lane with dual-lane configuration) using HS-G5 gear• Improved power efficiency: Lower power consumption per bit transferred compared to UFS 3.1• Enhanced thermal management: Better heat dissipation characteristics for sustained performance• Advanced features: Builds upon Write Booster, Deep Sleep, and HPB with further optimizationsUFS 4.0 is designed for next-generation flagship smartphones, tablets, and high-performance mobile devices requiring extreme storage bandwidth for 8K video recording, advanced computational photography, and AI workloads. Frequently Asked Questions about Flash Memory1. What are the different types of flash memory?Flash memory comes in two fundamental architectural types: NOR and NAND. NOR flash offers random access and execute-in-place capabilities, making it ideal for code storage. NAND flash provides higher density and faster write speeds, making it suitable for data storage. Within NAND flash, there are further subdivisions based on bits per cell: SLC (1 bit), MLC (2 bits), TLC (3 bits), and QLC (4 bits), each offering different trade-offs between performance, endurance, and cost. 2. What are the characteristics of flash memory?Flash memory has several distinctive characteristics: it is significantly less expensive than EEPROM and doesn't require batteries for data retention unlike SRAM. It is non-volatile, meaning data persists without power. Flash offers fast read access times (microseconds), high resistance to physical shock compared to hard disk drives, low power consumption, and silent operation. However, it has limitations including finite write/erase cycles, block-level erase requirements, and potential for bit errors requiring ECC. 3. What is the purpose of flash memory?Flash memory serves as a non-volatile storage solution widely used in embedded systems, consumer electronics, and enterprise storage. It retains data without power, can be electrically erased and reprogrammed, and offers advantages over traditional magnetic storage including faster access times, lower power consumption, better durability, and compact form factors. Flash memory evolved from EEPROM technology and has become the dominant storage technology for mobile devices, SSDs, USB drives, memory cards, and embedded systems. 4. What is the difference between NAND flash and NOR flash?NOR flash provides faster random read access and supports execute-in-place (XIP), allowing direct code execution without copying to RAM, making it ideal for firmware and boot code. However, it's more expensive and has slower erase/write operations. NAND flash offers higher storage density, lower cost per gigabyte, and much faster sequential write and erase speeds, making it ideal for mass storage applications. NAND is accessed serially through a shared I/O interface, while NOR has parallel address and data buses allowing random access. NAND requires more complex error correction due to higher bit error rates. 5. What is the difference between UFS and eMMC?UFS (Universal Flash Storage) is the successor to eMMC (embedded MultiMediaCard) and offers several significant advantages: UFS supports full-duplex operation allowing simultaneous read and write operations, while eMMC is half-duplex. UFS uses a faster serial interface with higher bandwidth (up to 11.6 GB/s in UFS 4.0 vs. 400 MB/s in eMMC 5.1). UFS also features command queuing for better multitasking performance, lower latency, and improved power efficiency. These advantages make UFS the preferred choice for modern flagship smartphones and high-performance mobile devices. 6. How does wear leveling work in flash memory?Wear leveling is a technique used to extend flash memory lifespan by distributing write and erase cycles evenly across all memory blocks. Since flash memory has a limited number of program/erase cycles per block, repeatedly writing to the same blocks would cause premature failure. Wear leveling algorithms track the erase count of each block and preferentially use blocks with lower erase counts for new writes. This ensures all blocks wear out at approximately the same rate, maximizing the overall device lifespan. Modern flash controllers implement sophisticated wear leveling algorithms as part of the Flash Translation Layer (FTL). 7. What is 3D NAND technology?3D NAND (also called V-NAND) is a flash memory architecture that stacks memory cells vertically in multiple layers, rather than arranging them in a single planar layer. This technology allows for higher storage densities without requiring smaller manufacturing process nodes. Modern 3D NAND implementations can have over 200 layers, significantly increasing capacity while improving performance and endurance compared to planar NAND. 3D NAND also offers better power efficiency and can achieve higher performance due to reduced cell-to-cell interference. This technology has become the standard for modern SSDs and high-capacity storage devices.

IntroductionThe hard disk interface is the connecting part between the hard disk and the host computer system, and its function is to transmit data between the hard disk cache and the host memory. Different hard disk interfaces determine the data transmission speed between the hard disk and the computer. In the entire system, the quality of the hard disk interface directly affects the speed of the program and the performance of the system. From this article, you can understand the connector concepts of IDE, SATA, SCSI, Fibre Channel (FC) and SAS and their development process, and finally two important interface protocols: AHCI and NVMe.SAS, SATA, SCSI, FC, and IDE ExplainedCatalogIntroductionⅠ Bus Interface TypesⅡ What is IDE?2.1 Integrated Drive Electronics Definition2.2 IDE Mode2.3 IDE Advantages and DisadvantagesⅢ What is SCSI?3.1 SCSI Basics3.2 SCSI VersionⅣ What is Fiber Channel (FC)?4.1 Overview of Fibre Channel4.2 Fibre Channel ProtocolⅤ What is SATA?5.1 Serial ATA Definition5.2 SATA Interface5.3 IDE vs SATA InterfaceⅥ What is M.2?Ⅶ What is SAS?Ⅷ Tech Guide: AHCI and NVMe Protocol8.1 AHCI Protocol8.2 NVMe Protocol8.3 Tech NoteⅠ Bus Interface TypesFrom an overall point of view, hard disk interfaces are divided into five types: parallel ATA (PATA, also called IDE or EIDE), SATA, SCSI, Fibre Channel, and SAS. IDE is mostly used in household products. And some of it are used in website servers. SCSI is mainly used in the server market. While Fibre Channel is only used in high-end servers and is expensive. SATA is now the mainstream hard disk. Most notebook computers and desktop computers use it, and solid state hard drives also use it. SAS is generally used in servers. It has fast transmission speed and strong reliability. Under the broad categories of IDE and SCSI, there has a variety of specific interface types that can be divided according to different technical specification and transmission speed. Ⅱ What is IDE?2.1 Integrated Drive Electronics DefinitionThe full name of IDE is "Integrated Drive Electronics", and its original meaning refers to the hard disk drive that integrates the "hard disk controller" and the "disk body". This approach reduces the number and length of cables for the hard disk interface, enhances the reliability of data transmission, and makes hard disk manufacturing easier. Many hard disks used to have IDE interfaces, but now almost all hard disk interfaces are standard with SATA.IDE represents a type of hard disk interfaces, but in actual applications, people are also used to call it the first IDE-type hard disk ATA-1. This type of interface has been eliminated with the development of technology. With the time passes, more types of hard disk interfaces are developed, such as ATA, Ultra ATA, DMA, Ultra DMA and other interfaces are all IDE hard disk interfaces.2.2 IDE ModeThere are three transmission modes for IDE: PIO (Programmed I/O), DMA (Driect Memory Access), and Ultra DMA (UDMA).The biggest drawback of PIO mode is that it consumes a lot of CPU resources. The IDE interface running in PIO mode has a data transfer rate ranging from 3.3MB/s (PIO mode 0) to 16.6MB/s (PIO mode 4). There are two types of DMA modes: Single-Word DMA and Multi-Word DMA. The highest transfer rate of Single-Word DMA mode is 8.33MB/s, and Multi-Word DMA (Double Word) can reach 16.66MB/s. The biggest difference between the DMA and the PIO is that the DMA mode does not rely too much on CPU instructions to run, which can save the processor's operating code.Due to the emergence and rapid popularity of the UDMA mode, PIO and DMA are immediately replaced by UDMA. UDMA is a standard protocol under the Ultra ATA system, which is based on the 16-bit Multi-Word DMA mode. One of the advantages of UDMA is that in addition to the advantages of DMA mode, it also applies CRC (Cyclic Redundancy Check) technology to enhance the performance of error detection and debugging during data transmission. Since the introduction of the Ultra ATA standard, its interface has applied DDR (Double Data Rate) technology to double the transmission speed, with a transmission speed of up to 100MB/s. 2.3 IDE Advantages and DisadvantagesAdvantages: Compatible and cost-effective.Disadvantages: slow data transmission speed, short cable length, fewer connected devices, no support for hot swap, poor upgrading ability of interface speed. Ⅲ What is SCSI?3.1 SCSI BasicsThe full name of SCSI is "Small Computer System Interface", which is a completely different interface from IDE. SCSI is not specifically designed for hard disks, but a high-speed data transmission technology widely used in minicomputers. It has the advantages of wide application range, multitask, large bandwidth, low CPU occupancy rate, and hot swap. So SCSI is mainly used in medium and high-end servers and high-end workstations. But the higher price makes it difficult to popularize like IDE. SCSI also has some potential problems. It has limited system BIOS support, and it has to be set for each computer. There's also no common SCSI software interface.Figure 1. SCSI Interface3.2 SCSI VersionSCSI VersionDescriptionsSCSI-1developed in 1986(obsolete)Introduced in 1979, supported synchronous and asynchronous SCSI peripherals.SCSI-2adopted in 1994Introduced in 1992, also known as fast SCSI, supported any SCSI device.SCSI-3debuted in 1995It is the standard currently in use. Ⅳ What is Fiber Channel (FC)?4.1 Overview of Fibre ChannelFibre Channel is the same as SCSI. It is not originally an interface technology developed for hard disk design and development, but specifically designed for network systems. However, as storage systems develop, they are gradually applied to hard disk systems. Fibre Channel is developed to improve the speed and flexibility of multi-disk storage systems. And it greatly improves the communication speed of multi-disk systems. The main characteristics of Fibre Channel are: hot swap, high-speed bandwidth, remote connection, large number of connected devices, etc. It can meet the high data transmission rate requirements of high-end workstations, servers, mass storage sub-networks, and peripherals for bidirectional and serial data communication through hubs, switches and point-to-point connection.4.2 Fibre Channel ProtocolFiber Channel ProtocolDescriptionsFC-0Physical layer, customizes different media, set transmission distance and signal mechanism standards, defines optical fiber, copper interfaces, and cable indicatorsFC-1Encode/DecodeFC-2Framing protocol /flow controlFC-3common services such as data encryption and compressionFC-4Protocol mapping layer, which defines the interface between fibre channel and upper-layer protocol. Upper-layer applications such as SCSI protocol, HBA FC-4 interface functions. FC-4 supports multiple protocols, such as FCP-SCSI, FC-IP, and FC-VI. Ⅴ What is SATA?5.1 Serial ATA DefinitionSATA stands for "Serial Advanced Technology Attachment" or "Serial ATA". It is an interface used to connect ATA hard drives to a computer's motherboard. SATA adopts serial connection mode. Serial ATA bus uses embedded clock signal, which has stronger error correction ability. Compared with the past, its biggest difference is that it can check transmission instructions (not just data). Errors are automatically corrected, which greatly improves the reliability of data transmission.Now the general interface is SATA interfaces. The reason why it can replace IDE is because the performance of the SATA is much better than that of the IDE. SATA speed is also much higher than IDE, and it also supports hot swap/hot-plugging.5.2 SATA InterfaceMost of the computers we use are also SATA interfaces. The current SATA interface has three versions 1.0, 2.0, and 3.0. The larger the version number, the later it appears, the better the performance, which mainly due to the faster data transfer rate. SATA 3.0 is the most common interface used today, though there have been four revisions since its introduction, namely 3.1 through 3.4. The SATA interface version is backward compatible, and the higher version is compatible with the lower. Some SATA hard disks provide jumpers. Due to the jumper settings are different, the version number of the SATA interface of the same hard disk is different. In addition, the actual transfer rate of the interface requires the support of the SATA motherboard.SSD has better performance, smaller size, and higher interface requirements. High-performance SSDs have basically switched to M.2, U.2 and PCIe, but SATA interfaces will not be eliminated in a short time. It is still in mainstream market, especially the HDD market. The SATA 3.3 specification upgraded by SATA-IO also brings some new features, optimizing the support of SMR, and can be powered off remotely. SMR shingled magnetic recording technology can increase the storage density of HDD by 25%.The SATA interface entered the 6Gbps era from the 3.0 standard in 2009. In 2011, SATA 3.1 was updated, SATA 3.2 was updated in 2013, and then SATA 3.3 was updated in 2016. These subversion upgraded have not brought many new functions. After all, the bottleneck of HDDs is not the speed, and it is difficult to make big improvements from the interface. 5.3 IDE vs SATA InterfaceSATA hard disk has a new design structure, fast data transmission, save space, and many other advantages over IDE hard disk:1) SATA hard disk has a higher transmission speed than IDE hard disk. SATA can provide a peak transfer rate of 150MB/s. It will reach 300 MB/s and 600 MB/s with the development. At that time, we will get a transfer rate nearly 10 times faster than IDE hard drives.2) Compared with the PATA40-pin data cable of IDE hard disks, the SATA cable is small and thin. And the transmission distance is long, which can be extended to 1 meter, making it easier to install equipment and wiring in the machine. Because the size of the connector is small, this kind of cable effectively improves the air flow inside the computer and also speedsthe heat dissipation in the case.3) Thepower consumption has been reduced. SATA hard drives can work with 500 mA of current.4) SATA can be backward compatible with PATA devices by using multi-purpose chipsets or serial-parallel converters. Since SATA and PATA can use the same drive, there is no need to upgrade or change the operating system.5) SATA does not need to set the master and slave disk jumpers. The BIOS will number it in the order of 1, 2, 3. Whilethe IDE hard disk needs to set the master and slave disks through jumpers.6) SATA also supports hot plugging and can be used like a U disk. IDE hard disks do not support hot swap. Ⅵ What is M.2?The M.2 interface is a new interface specification. It is a new standard tailored for Ultrabooks to replace the original mSATA interface. Whether it is a smaller size or higher transmission performance, M.2 is far better than mSATA.M.2 interfaces are generally divided into two types. When buying M.2 SSDs, you need to pay attention to internal agreements. One is to use the traditional SATA AHCI protocol, which has no difference in performance with ordinary SATA solid hard drives; another is to use the brand-new NVMe protocol, which can provide SSD performance up to 3000MB/s or more. Ⅶ What is SAS?SAS (Serial Attached SCSI) is a new generation of SCS technology, which is the same as the current popular SATA technology. It uses serial technology to obtain higher transmission speed and improves internal space by shortening the cable. SAS is a new interface developed after the parallel SCSI. This interface is designed to improve the performance, availability, and expandability of the storage system, and to provide compatibility with the SATA.SAS technology can be backward compatible with SATA. Specifically, the compatibility of the two is mainly reflected in the compatibility of the physical part and the protocol. At the physical layer, the SAS interface and the SATA interface are fully compatible, and the SATA hard disk can be directly used in the SAS environment. In terms of interface standards, SATA is a sub-standard of SAS, so the SAS controller can directly control SATA hard drives, but SAS cannot be directly used in the SATA environment. Because the SATA controller cannot control the SAS hard disk. As for the protocol, SAS is composed of three types of protocols, which use corresponding protocols for data transmission according to different devices. Among them, the serial SCSI protocol (SSP) is used to transmit SCSI commands, the SCSI management protocol (SMP) is used to maintain and manage connected devices, and the SATA channel protocol (STP) is used to transfer data between SAS and SATA. Therefore, under the cooperation of three protocols, SAS can seamlessly work with SATA and some SCSI devices.The backplane of the SAS system can be connected to dual-port, high-performance SAS drives and high-capacity, low-cost SATA drives. So SAS drives and SATA drives can exist in a storage system at the same time. But it should be noted that the SATA system is not compatible with SAS, so SAS drives cannot be connected to the SATA backplane. Due to the compatibility of the SAS system, users can use hard drives with different interfaces to meet the capacity or performance requirements of various applications. So they have more flexibility when expanding the storage system, allowing storage devices to maximize application benefits.In the system, each SAS port can connect up to 16256 external devices, and SAS adopts a point-to-point serial transmission directly with a transmission rate of up to 3Gbps. It is estimated that there will be 6Gbps or even 12Gbps high-speed interfaces in the future. The SAS interface performance has also been greatly improved. It also provides 3.5-inch and 2.5-inch interfaces, so it can meet the requirements of different server environments. SAS relies on SAS expanders to connect more devices. Most expanders have 12 ports.Compare with the traditional parallel SCSI, SAS has a significant increase in interface speed. With the use of serial cables, it not only can achieve a longer connection distance, but also improve the anti-interference ability. In addition, this cable can also significantly improve the heat dissipation inside the chassis. Ⅷ Tech Guide: AHCI and NVMe ProtocolHere we will focus on the AHCI protocol and NVMe protocol of the solid state drive (SSD).There are two mainstream transmission protocols for SSD (Solid State Drive): One is the AHCI protocol, and the other is the NVMe protocol.8.1 AHCI ProtocolAdvanced Host Controller Interface (AHCI), sets the operation of Serial ATA (SATA) host controllers in a non-implementation-specific manner in its motherboard chipsets. That is, AHCI allows storage drivers to connect advanced SATA functions. When we use SATA SSD, we must enable AHCI mode in the motherboard settings. This is because when the AHCI mode is turned on, the number of useless seeks of the SSD can be greatly shortened and the data search time can be reduced. So that the SSD under multi-tasking can exert all the performance and effects. According to related performance tests, after the AHCI mode is turned on, the SSD read and write performance is increased by about 30%. However, with the gradual enhancement of SSD performance, these standards have also become a major bottleneck restricting solid state drives. Because the AHCI standard designed for hard disk drives is not suitable for low-latency solid state drives.8.2 NVMe ProtocolAnother transmission protocol is the NVMe protocol that represents the future performance trend. The so-called NVMe protocol is to make full use of the low latency and parallelism of PCI-E channels, greatly improve the read and write performance of SSDs under controllable storage costs. It reduces the high latency caused by the AHCI, and completely liberates ultimate performance of SATA SSD.NVMe Specification1.0 (March 2011)1.1 (October 2012)1.2 (November 2014)Fabric's NVMe (2014)NVM-MI (November 2015)1.3 (April 2017)1.4 (July 2019)Due to the flash memory particles and the main control, the SSD(solid state drives) price with M.2 NVMe protocol is very high, which is about twice the price of SATA SSD. So buy the corresponding level of solid state hard drive based on the configuration and requirements of the computer. Otherwise it will cause performance waste.In terms of software layer, the delay of NVMe standard is less than half of AHCI. NVMe streamlines the calling method and does not need to read registers when executing commands. Each command of AHCI needs to read registers 4 times, which consumes 8000 CPU times in total loop, causing a delay of about 2.5 ms. NVMe can support receiving commands and prioritizing requests from multi-core processors at the same time.NVMe has automatic power state switching and dynamic power management functions. The device can switch to Power State 1 after being idle for 50ms from Power State 0. If it continues to be idle, it will enter Power State 2 with lower power consumption after 500ms. There will be a short delay when switching. The SSD can be controlled at a very low level when it is idle. In terms of power management, the NVMe SSD will have a greater advantage than the AHCI SSD. This is important for mobile devices, which can significantly increase the power endurance of notebooks. Moreover, NVMe SSD can be easily matched to different platforms and systems, and can work normally without the corresponding driver provided by the manufacturer. At present, Windows, Linux, Solaris, Unix, VMware, UEFI, etc, support the NVMe SSD.PCIe SSDs based on the NVMe protocol far exceed the traditional AHCI-based SATA SSDs in terms of performance and practicability. It can be said to be the future of the development of the SSD industry. But the traditional SATA interface will become the first choice for ordinary machine installations under the background of reduced manufacturing costs.8.3 Tech Note8.3.1 PCI-E BasicPCI-E (peripheral component interconnect express) is a high-speed serial computer expansion bus standard. Its original name is "3GIO". It was proposed by Intel in 2001 to replace the old PCI, PCI-X, and AGP bus standard. It belongs to high-speed serial point-to-point high-bandwidth dual-channel transmission. The connected devices allocate exclusive channel bandwidth and do not share bus bandwidth. It mainly supports active power management, error reporting, end-to-end reliable transmission, hot plugging, quality of service ( QOS), and other functions. PCI-E also has a variety of specifications, from PCI-E x1 to PCI-E x32, which can meet the needs of low-speed devices and high-speed devices in a certain period of time in the future.The PCI-E bus protocol can be directly connected to the CPU with almost no delay, making it an excellent companion to the NVMe standard. In the era of the AHCI standard, the actual performance of PCIe can hardly be exerted due to the agreement limit.Table: PCle VersionVersionYearDescriptionPCIe 1.0a2003The data rate per channel is 250 MB/s, and the transmission rate is 2.5 GT/s.PCIe 1.12005The data rate has not changed and it is fully compatible with PCIe 1.0a.PCIe 2.02007It doubles the transfer rate from PCIe 1.0 to 5 GT/s, and the throughput per channel rises from 250 MB/s to 500 MB/s.PCIe 2.12009Its speed is the same as PCIe 2.0, supporting troubleshooting system.PCIe 3.02010Transmitter and receiver equalization, PLL improvements, clock data recovery, and channels are all improved.PCIe 3.12014Various improvements based on the PCIe 3.0 specifications.PCIe 4.02016Double the bandwidth provided by PCIe 3.0, maintain software support, and have backward compatibility for the used mechanical interfaces.PCI-E SD 7.02018A new generation of SD 7.0 standard specifications 8.3.2 Interface Size IntroductionThe size and application of the hard disk can be divided into:0.85 inches, mostly used in portable devices such as mobile phones.1 inch, mostly used in digital cameras (CF type II interface).1.8 inches, used in some notebook computers and external hard disk enclosures.2.5 inches, commonly used in notebook computers and external hard disk enclosures.3.5 inches, mostly used in desktop computers. External hard drive enclosures with 3.5-inch requires an external power supply. Frequently Asked Questions about Hard Disk Drive Interface1. Which is a hard disk interface?Today's hard drives use SATA or SAS interfaces, which are the serial versions of their PATA and SCSI predecessors. SATA drives are found in every personal computer, and SAS drives, which are enterprise class, are found in servers and high-end workstations. 2. What are the three most common types of hard drive interfaces?There are three different kinds of hard drives: SATA, SSD and NVMe. 3. What is the fastest hard drive interface?PCIe provides a faster interface speed than SATA. An SSD connected via a PCIe 3.0 x16 interface can have a link speed of 16 Gb/s. In contrast the SATA 3.0 standard only provides 6.0 Gb/s. Solid State Drives (SSDs) come in a number of different form factors and are available with different interface connects. 4. What are the types of drive interfaces?Hard disk drives are accessed over one of a number of bus types, including parallel ATA (PATA, also called IDE or EIDE; described before the introduction of SATA as ATA), Serial ATA (SATA), SCSI, Serial Attached SCSI (SAS), and Fibre Channel. 5. What is PATA hard disk?Parallel ATA (Parallel Advanced Technology Attachment or PATA) is a standard for connecting hard drives into computer systems. As its name implies, PATA is based on parallel signaling technology, unlike serial ATA (SATA) devices that use serial signaling technology. 6. Can I connect a SATA hard drive to an IDE motherboard?Yes now you can connect the SATA hard drive to an IDE motherboard very easy. Just visit your near computer hardware shop or amazon to search “SATA bilateral IDE” card. This card will covert the SATA hard desk to IDE. After this your hard desk can be connected IDE motherboard. 7. Why is SCSI still used?It's a fast bus that can connect lots of devices to a computer at the same time, including hard drives, scanners, CD-ROM/RW drives, printers and tape drives. Other technologies, like serial-ATA (SATA), have largely replaced it in new systems, but SCSI is still in use. 8. Can I replace an ATA drive with a SATA drive?Replacing the ATA drive with a SATA drive you will need the SATA drivers for your system unless the bios is set to IDE emulation. Windows won't recognize the drive without the drivers installed or IDE emulation turned on. 9. Is NVMe and M 2 the same?NVMe stands for Non-Volatile Memory Express, and it refers to the way in which data is moved, rather than the shape of the drive itself. ... There are some NVMe drives that are designed to fit into a standard PCIe motherboard slot much like a graphics card, but most NVMe drives use the M. 2 form factor. 10. What is a m2 SATA drive?M. 2 is a form factor for SSDs (solid-state drives) that's shaped like a stick of gum. These SSDs are generally faster but more expensive than traditional, 2.5-inch SSDs. Thin laptops are increasingly using M. 2 SSDs because they take up less room than 2.5-inch SSDs or hard drives.

Ⅰ IntroductionIn recent years, with the rapid development of the internet of things (IoT) and electronic technologies, embedded devices such as mobile phones, smartwatches, and sports bracelets have become important elements of cloud computing, IoT, and big data analytics. Embedded terminal devices become more usual in daily life. However, to meet the high storage requirements of these increasingly diverse applications, scientific research personnel face more challenges. Non-volatile memory is more and more popular in the market due to its advantages such as low energy consumption, non-volatile, high density, and low latency. The following is a basic introduction to new non-volatile memory with good future development prospects.The Future of Non-volatile MemoryCatalogⅠ IntroductionⅡ TerminologyⅢ Concept and ClassificationⅣ One Question Related to Non-volatile Memory and Going Further4.1 Question4.2 AnswerⅡ TerminologyMemory is an important part of computer systems. According to different positions in the storage system, memory can be simply divided into three types: on-chip memory, main memory, and hard disk. Correspondingly, static memory (SRAM), dynamic memory (DRAM), and magnetic disks have become the traditional technologies to realize these storage system. Over the past 40 years, these three technologies have achieved tremendous technical and commercial success. With the exception of magnetic disks, the manufacture of both static and dynamic memory relies on semiconductor integration technology. Although these two technologies are different, they also have a common characteristic: they both use the accumulation and release of charge on semiconductor devices to achieve data storage. For example, in a dynamic memory, the charge is used to represent a logic 1, and the discharge represents logic 0. In static memory, this process is achieved by charging and discharging the parasitic capacitance of the transistor. For example, solid-state storage, which widely used in flash memory, also stores data by capturing and releasing the charge on the floating gate of the transistor.With the improvement of manufacturing technologies, the size of semiconductor nano devices has continued to shrink, and the charges that can be stored on all of the above traditional memory devices has also decreased, which has brought serious reliability issues: First, more leakage current; second, a small perturbation of charges will have a relatively greater impact. In addition, the inherent limitations of the charge storage mechanism itself also can't be avoided, the processing of traditional mainstream memories at the nanoscale and the process disturbances are also very challenging.From the aspect of functions, static memory and dynamic memory both belong to the volatile memory category. Its characteristic is that when the power supply is off, the data stored in the memory will disappear and cannot be recovered. Especially in the design of dynamic memory, the charge on the capacitor will gradually leak out as the time increases. Therefore, the stored info need to be refreshed periodically. The static memory doesn't have this issue, but the area of the memory cell is usually large (about 20 times that of the dynamic memory cell), causing serious leakage current. Flash memory belongs to the non-volatile memory, and the data stored on it will be retained for a long time after the power off. In terms of performance, the first two types of memory read & write speed are on the level of nanoseconds, while the flash memory are on the level of hundreds of microseconds or even milliseconds. For the reading mode, the static memory and the dynamic memory can achieve random storage, for example, any one or several memory cells can be read and written at will. It different for Flash, although its storage density is high, the read operation must be performed in units of pages. Moreover, the content update of the flash memory cannot be achieved by directly overwriting the original content, but must be written to a new erased page. In addition, the maximum times of read and write supported by flash memory is extremely limited, typically between thousands of and millions of times. Ⅲ Concept and ClassificationConcept: Non-volatile memory refers to the computer memory of the person whose stored data will not disappear when the power is turned off. It is characterized by non-volatile, byte-by-byte access, high storage density, low energy consumption, and fast read and write speed, but the read speed  far faster than write, in other words, they are asymmetric in a limited life.Classification: According to whether the data in the memory can be rewritten at any time, the traditional non-volatile memory can be divided into two categories: read-only memory (ROM) and Flash memory. New type non-volatile memory compared with traditional non-volatile memory, its device has greatly improved energy consumption, read and write speed, integration density, etc. At present, the newly developed new non-volatile memory mainly includes four types: dielectric memory (FRAM), magnetic medium memory (MRAM), Ovonic phase change memory (OUM), and polymer memory (PFRAM).The following highlights four new non-volatile memories.The technical limitations of traditional memories and the huge challenges brought by the light weight have prompted researchers to look for a new generation of memory devices. People want to find a memory with the following characteristics:1) Nano level read and write speed of static memory2) Integrated density with dynamic memory and even flash memory level3) Flash-like non-volatile memory featuresAlthough such a storage technology has not been fully realized at present, some very promising new storage devices have been developed, and some have even entered the production stage. The four newly developed non-volatile memories are very promising for data processing, because of the limitations of traditional non-volatile memories, it is very likely to replace flash memory in the future.Table 1. New Non-volatile Memories Basic SituationsItemPerformanceManufactureLimitationApplicationFerroelectric RAM(FRAM)1) low energy consumption 2) high read & write speed3) long storage time4) low power operation5) anti-radiationsmaller size1) limit read & write times2) low storage density3) low reliability1) RF IC card2) fast-start memory3) embedded cache4) aerospaceMagnetic RAM(MRAM)1) high read & write speed 2) unlimited read & write times3) low power operationsimple circuithigh cost1) storage2) industrial automation, 3) games 4) energy management 5) communication 6) transportation7) aerospace electronics8) sensor terminalsPhase Change Memory (OUM) 1) long service life2) safety 3) low energy consumption1) small capacity2) low cost1) lower read &write speed2) poor temperature characteristic1) wired and wireless communications2) consumer electronics 3) PC and embedded devicesPolymeric RAM1) good stability 2) low power operation1) 3D stack2) easy processing3) low cost1) limit read & write times, 2) destructiveness1) PC 2) digital camera 3) mobile phoneFRAMa. IntoductionFRAM is the non-volatile memory technology in the new generation. In terms of performance, it consumes low energy and can store data for a long time although there is power failure. It combines the characteristics of high read-write speed of RAM and long-term data storage of ROM. Embedded FRAM in the non-volatile memory situation of radiation-resistant and low-power has great significance. It can be embedded in the chip in a more direct way and has better performance than any other alternative chips. In terms of manufacturing and technology, FRAM is easier to reduce size than flash memory due to the advanced nodes (65 nm or smaller), and does not require the use of very thin oxides or high voltages. b. LimitationWhen FRAM reaches a certain times of read and write, FRAM cells will lose their durability, and the FRAM yield problem caused by array size restrictions and further improvements in storage density and reliability still need to be resolved.c. ApplicationFRAM is a non-volatile memory that combines the advantages of low power consumption, high speed, long service life, and anti-radiation. It is promising in RF 1C card, fast startup memory, and system chip of cache and aerospace.d. Commercial progressFrom the point of international respect, well-known American company Ramtorn, which developed the first 4K bit commercial ferroelectric memory in 1993; after 1998, Ramtorn focused on product research and development, and handed over all production to semiconductor manufacturers. With the time goes by, Ramtorn represents the highest level of PZT-based commercial ferroelectric memory. Many other countries started late in the field of ferroelectric research and mainly based on scientific research. For example, the main work of some countries is still the preparation of ferroelectric thin films. MRAMa. MRAM BasicsMRAM is a non-volatile memory. For the performance, the write speed of MRAM is extremely fast, almost 1000 times that of flash memory, and 20 times that of FRAM. And it has unlimited read and write times, also it can switch on and off instantly and extend the battery life of portable computers. In terms of manufacturing and technology, the circuit of MRAM is simpler than ordinary memories, and only one readout circuit is needed for chip access. In addition, MRAM is easier to integrate (only 5 photomask layers are needed in the entire process), and there is no need to redesign at the transistor level of flash memory. All other core technologies used in the design can remain the same and work consistently.From 1986 to 1988, Albert Fert and Peter Grünberg discovered that nano-multilayer films composed of alternating ferromagnetic and non-magnetic metal layers made of molecular beam epitaxy have a much larger size than AMR, which is named as giant magnetoresistance (GMR). GMR is a quantum mechanical magnetoresistance effect observed in multilayers composed of alternating ferromagnetic and non-magnetic conductive layers, but it was difficult to put into practice. Soon, further research by Parkin team found that the (ferromagnetic / non-magnetic metal / ferromagnetic) three-layer film made by sputtering technology has a much larger giant magnetic resistance at room temperature than a single-layer ferromagnetic metal. For the spin valve, opened the way for practical use of GMR.The discovery and research of GMR had led to the realization of high-sensitivity read heads in high-density disks, and promoted the development of the entire modern hard disk industry. The earliest application of spin valve sensors in hard disk read heads was in the IBM Deskstar 16GP Titan, which was released in 1997 and has a storage capacity of 16.8GB. In 2007, Hitachi introduced the Deskstar 7K1000, the first 1TB hard drive.b. MRAM LimitationMRAM is much higher than flash memory in the production costs.c. MRAM ApplicationWith the advantages of low power consumption, high-speed reading, high integration, radiation resistance and unlimited rewrites, MRAM is used in storage, industrial automation, gaming, energy management, communications, consumption electronic,transportation and avionics fields. In addition, the IOT and big data analytics are gradually emerging,ubiquitous sensor terminals need to collect massive amounts of data, in order to save storage power consumption, MRAM and STT-MRAM have become the better choices for their relatively good performance.d. MRAM Commercial ProgressIn 2006, Freescale launched the world’s first commercial MRAM product with a capacity of 4Mb. Judging from the current product specifications and development status, the use of MRAM is still limited to some specific markets. From the perspective of cost and capacity, it cannot compete with NAND flash memory with a maximum capacity of 8Gb and DRAM with 512Mb capacity. However, with Samsung, Intel, TSMC and Global Foundry and other integrated circuit leaders strengthening investment in R & D and related production lines, STT-MRAM is gradually begin mass production, partially replacing SRAM and DRAM products and becoming one of the mainstream memories. OUMa. OUM BasicPhase change memory is a kind of memory that realizes information storage through material phase change. It is the non-volatile and large-capacity storage technology advocated by Intel, the world's number one semiconductor chip manufacturer. In terms of performance, it has a long read and write operation life and is easier to integrate than flash memory. OUM memory cells are extremely dense, and read operations is more safer than other memories. Low energy consumption, requiring very low power to operate. In addition, OUM unit can write about 1 billion times, which makes it an ideal alternative to large-capacity memory in portable devices. From the aspect of manufacturing process, compared with the integration of existing logic circuits, its storage unit is only 1/3 of MRAM and FRAM, and its production cost is lower than other new memories.Crystalline Phase and Amorphous Phase ChangeAlthough phase change memory is often categorized as “new memory”, the concept of “phase change” has introduced over 50 years. In 1962, the phase transition of As-Te glass was discovered. In 1968, Stanford Robert Ovshinsky described in an article that certain semiconductor materials can rapidly switch between two different states of resistance and conductivity under the action of an electric field (on the order of 10μs), he utilized chain structures, cross links, polymeric concepts, and divalent structural bonding with a huge number of unbonded lone pairs to achieve what is now referred to as the “Ovshinsky Effect”, an effect that turns special types of glassy, thin films into semiconductors upon application of low voltage. This discovery directly led to a large number of subsequent studies on the phase transition of thin films based on tellurium-arsenide-germanium-silicon alloy materials or sulfur-based glasses. In 1970, Nevill and Gordon Moore demonstrated the world’s first 256-bit phase change memory, and Moore was later known for putting forward the famous “Moore's Law” about the number of transistors in a dense integrated circuit doubles about every two years and served as the co-founder of Fairchild Semiconductor and CEO of Intel. After that, research on semiconductor memories based on phase change materials has gradually slowed down due to issues such as materials and power consumption, but phase change materials have been used very successfully in rewritable optical discs such as CD-RW / DVD-RW.   b. OUM LimitationThe read and write speed and frequency of OUM are not as good as FRAM and MRAM, and how to maintain its driving temperature stably is also a big technical problem.c. OUM ApplicationPhase change memory is suitable for wired and wireless communication equipment, consumer electronics, PC and other embedded applications due to its fast read and write speed, strong upgrade capabilities, and low power consumption. For example, it is used in the aerospace embedded system and used in smart meters to further integrate its storage architecture.d. OUM Commercial ProgressPhase change memory, as one of the most promising new memories, can be embedded at all levels of the memory architecture. Because of the similarity between phase change memory and dynamic memory, especially its lower power consumption and scalability, it has been considered as the best substitute for dynamic memory. But phase change memory also has disadvantages. The first is its limited times of erases and writes (usually only 107 to 108). If the number of erasing and writing exceeds this limit, the life of the memory cell will end, and the device can no longer be used. The second disadvantage is the limited write speed. The write speed of phase change memory is 6-10 times slower than dynamic memory. Write Operation of Phase Change Memory UnitNevertheless, phase change memory still has good applications in some fields. Several related studies have proposed various methods to overcome these shortcomings. For example, an architecture adjustment is used to compensate for the loss caused by the performance of writing, which can greatly reduce power consumption, thereby accelerating the commercialization of phase change memory as the main memory of a computer.In addition, the multi-level cell technology has been successfully implemented on phase change memory. In the design of a multi-level cell phase change memory, 2N resistive states are used to represent N digits, respectively, in other words, in a 2-bit multi-level cell phase change memory, 00, 01, 10, and 11 can be represented by four different resistance values, respectively. In the specific design, the resistance of the phase change material can be changed by adjusting the amplitude and time of the writing current / voltage. PFRAMa. PFRAM BasicsPFRAM is a plastic, polymer-based, and non-volatile memory. In terms of performance, PFRAM has advantages such as good stability and low power consumption. From manufacturing process, high density can be obtained through three-dimensional stacking technology, which is easy to make and has extremely low manufacturing costs, only about 10% of NOR-type flash memory.b. PFRAM LimitationPFRAM has a limited read and write operation life and its reads are destructive.c. PFRAM ApplicationThe final product of (PFRAM will be an all-organic storage system, which will be suitable for personal computers, handheld computers, digital cameras, mobile phones, handheld radios and communication devices, GPS systems, audio, video, game background program and other important fields.d. PFRAM Commercial ProgressPFRAM develops slowly in commercial use, and Intel is in a leading position. In 2014, Intel recruited JonKrueger (architecture and software engineer) to work for its polymer memory group and greatly promote the development of multi-layer plastic memory, finally their work is close to the software development stage, which indicates that this memory technology will accelerate to the market.Memory technology will continue to improve to meet different applications. On the one hand, The new type memories will create a new market and enter various application markets, on the other hand, it involves new materials and research concepts, it will be difficult to become the mainstream of the market in a long time. However, in the aerospace, industrial automation,  embedded cache of system chip and other sub-application areas, the new non-volatile memory will gradually transfer its technological breakthroughs to market penetration and achieve rapid development.With the advent of the 5G era, the development of application markets such as the IOT, artificial intelligence, and smart cities, and the urgent need for diverse memory requirements, coupled with traditional memory market change, new type memories will play an increasingly important role in the market. Ⅳ Questions Related to Non-volatile Memory and Going Further 1. Which memory is called non-volatile memory?Examples of non-volatile memory include read-only memory (see ROM), flash memory, most types of magnetic computer storage devices (e.g. hard disks, floppy discs and magnetic tape), optical discs, and early computer storage methods such as paper tape and punched cards. 2. Which is non-volatile memory RAM or ROM?RAM, which stands for random access memory, and ROM, which stands for read-only memory, are both present in your computer. RAM is volatile memory that temporarily stores the files you are working on. ROM is non-volatile memory that permanently stores instructions for your computer. 3. What is another name for non-volatile memory?Non-volatile memory (NVM) or non-volatile storage is a type of computer memory that can retain stored information even after power is removed. 4. Which is the most non-volatile memory?NAND flash, the most common type used in data storage, includes several variants, such as single-level cells or one bit per multi-level cell or two bits per cell; three-level cells or three bits per cell and quad-level cells or four bits per cell, respectively. 5. What is non-volatile memory explain with example?NV or non-volatile memory is a term used to describe memory or storage that is saved regardless if the computer has power. ... An example of non-volatile memory and storage is a computer hard drive, flash memory, and ROM.

SummaryRecently engineers discover the two-dimensional atomic sheets for memory storage when they were developing alternative ways to provide greater memory storage capacity on thiner computer chips. Most of us are curious about how engineers discover them?DiscoverA team of electrical engineers at The University of Texas at Austin, in collaboration with Peking University scientists, has developed the thinnest memory storage device with dense memory capacity, paving the way for faster, smaller and smarter computer chips for everything from consumer electronics to big data to brain-inspired computing. Discussion"For a long time, the consensus was that it wasn't possible to make memory devices from materials that were only one atomic layer thick," said Deji Akinwande, associate professor in the Cockrell School of Engineering's Department of Electrical and Computer Engineering. "With our new 'atomristors,' we have shown it is indeed possible." Made from 2-D nanomaterials, the "atomristors"—a term Akinwande coined—improve upon memristors, an emerging memory storage technology with lower memory scalability. He and his team published their findings in the January issue of Nano Letters. "Atomristors will allow for the advancement of Moore's Law at the system level by enabling the 3-D integration of nanoscale memory with nanoscale transistors on the same chip for advanced computing systems," Akinwande said.Memory storage and transistors have, to date, always been separate components on a microchip, but atomristors combine both functions on a single, more efficient computer system. By using metallic atomic sheets (graphene) as electrodes and semiconducting atomic sheets (molybdenum sulfide) as the active layer, the entire memory cell is a sandwich about 1.5 nanometers thick, which makes it possible to densely pack atomristors layer by layer in a plane. This is a substantial advantage over conventional flash memory, which occupies far larger space. In addition, the thinness allows for faster and more efficient electric current flow.Given their size, capacity and integration flexibility, atomristors can be packed together to make advanced 3-D chips that are crucial to the successful development of brain-inspired computing. One of the greatest challenges in this burgeoning field of engineering is how to make a memory architecture with 3-D connections akin to those found in the human brain. "The sheer density of memory storage that can be made possible by layering these synthetic atomic sheets onto each other, coupled with integrated transistor design, means we can potentially make computers that learn and remember the same way our brains do," Akinwande said. The research team also discovered another unique application for the technology. In existing ubiquitous devices such as smartphones and tablets, radio frequency switches are used to connect incoming signals from the antenna to one of the many wireless communication bands in order for different parts of a device to communicate and cooperate with one another. This activity can significantly affect a smartphone's battery life. The atomristors are the smallest radio frequency memory switches to be demonstrated with no DC battery consumption, which can ultimately lead to longer battery life. All in all,this discovery has real commercialization value as it won't disrupt existing technologies. Rather, it has been designed to complement and integrate with the silicon chips already in use in modern tech devices.  

With the rapid increase in production of intermittent energy sources such as wind and solar, there is an increasing need for large-scale electrical energy storage systems to more efficiently match supply and demand for these renewable sources. Also, large-scale energy storage can increase the annual load factor (defined as the annual mean power divided by the maximum three-day mean power) by load leveling. Traditionally, pumped-hydro has been used for load leveling at large scale plants, but this is geographically limited to a small subset of locations.Flow batteries are especially attractive for these leveling and stabilization applications for electric power companies. In addition, they are also useful for electric power customers such as factories and office buildings that require increased capacities, uninterrupted supply, or backup power.And how much do you know anything about flow battery?  Flow BatteryA flow battery is a type of rechargeable battery where rechargeability is provided by two chemical components dissolved in liquids contained within the system and most commonly separated by a membrane. This technology is akin to both a fuel cell and a battery - where liquid energy sources are tapped to create electricity and are able to be recharged within the same system. One of the biggest advantages of flow batteries is that they can be almost instantly recharged by replacing the electrolyte liquid, while simultaneously recovering the spent material for re-energization. Different classes of flow cells (batteries) have been developed, including redox, hybrid and membraneless. The fundamental difference between conventional batteries and flow cells is that energy is stored as the electrode material in conventional batteries but as the electrolyte in flow cells.  A rechargeable battery to power a home from rooftop solar panelsRecently scientists have said that a rechargeable battery that could make storage of electricity from intermittent energy sources like solar and wind safe and cost-effective for both residential and commercial use. The new research builds on earlier work by members of the same team that could enable cheaper and more reliable electricity storage at the grid level. The mismatch between the availability of intermittent wind or sunshine and the variability of demand is a great obstacle to getting a large fraction of our electricity from renewable sources. This problem could be solved by a cost-effective means of storing large amounts of electrical energy for delivery over the long periods when the wind isn't blowing and the sun isn't shining. In the operation of the battery, electrons are picked up and released by compounds composed of inexpensive, earth-abundant elements (carbon, oxygen, nitrogen, hydrogen, iron and potassium) dissolved in water. The compounds are non-toxic, non-flammable, and widely available, making them safer and cheaper than other battery systems.  "This is chemistry I'd be happy to put in my basement," says Michael J. Aziz, Gene and Tracy Sykes Professor of Materials and Energy Technologies at Harvard Paulson School of Engineering and Applied Sciences (SEAS), and project Principal Investigator. "The non-toxicity and cheap, abundant materials placed in water solution mean that it's safe—it can't catch on fire—and that's huge when you're storing large amounts of electrical energy anywhere near people." This new rechargeable battery chemistry was discovered by post-doctoral fellow Michael Marshak and graduate student Kaixiang Lin working together with co-lead author Roy Gordon, Thomas Dudley Cabot Professor of Chemistry and Professor of Materials Science at Harvard. "We combined a common organic dye with an inexpensive food additive to increase our battery voltage by about 50 percent over our previous materials," says Gordon. The findings "deliver the first high-performance, non-flammable, non-toxic, non-corrosive, and low-cost chemicals for flow batteries." Unlike solid-electrode batteries, flow batteries store energy in liquids contained in external tanks, similar to fuel cells. The tanks (which set the energy capacity), as well as the electrochemical conversion hardware through which the fluids are pumped (which sets peak power capacity), can be sized independently. Since the amount of energy that can be stored can be arbitrarily increased by scaling up only the size of the tanks, larger amounts of energy can be stored at lower cost than traditional battery systems.  Application&BenefitsThe main benefits of flow batteries can be aggregated into a comprehensive value proposition.The main features that distinguish flow batteries are:  Long service life: The semi-permanent electrolyte combined with minimal electrode degradation allows for a high number of full charge-discharge cycles before replacement is needed. The electrodes do not undergo physical/chemical changes, so they can be optimized for catalytic and electrical properties without having to design for holding active substances. Also, convective cooling of the electrodes by the pumped electrolyte aids in heat distribution and management. No standby loss: During prolonged gaps in use, there is little self-discharge since the charge-carrying electrolyte is stored in separate tanks. Low maintenance: The charge state of each cell is the same since the same electrolyte is used for all cells, thus overcharging is not necessary to guarantee a uniform a charge. Recyclability & Safety: Waste vanadium can be reused and cross-contamination across the positive and negative electrode compartments does not affect the composition. Also, the electrolytes are relatively nontoxic. Charging characteristics: Redox flow batteries are "not affected by fluctuating power demand, repeated total discharge, or charge rates as high as the maximum discharge rates."  These actions severely reduce cycle life in other batteries. Modularity: Perhaps most important is that energy capacity can be scaled independently of the power; cell characteristics such as electrode area do not need to be changed to modify capacity. This allows for underground storage of electrolyte in freeform tanks, which has been demonstrated successfully in a 20 kW system. Ref.KY605-BP12-12-T2KY605-EB50-12-I2