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Memory (DRAM) and SSD glossary

BIOS, CMOS, mSATA ... does this make you scratch your head and say "what"? Not everyone understands every technical term used today and we at Crucial understand. Our expert team compiled this list of memory (DRAM) and SSD terms to create a glossary that makes technical terms understandable through everyday words.



Title Description
Access Time The amount of time it takes to access data from a memory cell. Usually measured in nanoseconds (ns).
Alignment Refers to the partition alignment of a storage device. Alignment determines the starting position of a partition to ensure optimal read/write performance.
Antistatic A term used to describe something that prevents electrostatic discharge, such as an antistatic bag.
App Application is a computer program designed for a specific task or use. Microsoft© Word© is a word processing application.
BIOS Basic input/output system. Often referred to as CMOS, the BIOS provides an interface for a computer's hardware and software. The BIOS determines how your hardware is accessed.
Bandwidth The amount of data that can be moved between two pieces of hardware in a given period of time. The bandwidth of DRAM modules is measured in megatransfers per second (MT/s).
BSOD (Blue Screen of Death) A blue screen displaying a crash or error message on a Windows-based system.
Bandwidth The amount of data that can be moved between two points in a given period of time. The bandwidth of DRAM modules is measured in Megabytes per second (MB/s).
Binary A computer numbering system based on two digits: 0 and 1. All information in a computer is stored and transferred in binary.
Bit Binary digit. The smallest piece of data (a 0 or a 1) that a computer recognizes.
BSOD Blue screen of death is a blue screen displaying a crash or error message on a Windows-based system.
Buffer A holding area for data shared by devices that operate at different speeds or have different priorities. A buffer allows a device to operate without the delays that other devices impose.
Bus A path in a computer used to move data. A data bus is described in terms of its width (in bits) and its speed (in megahertz). The front-side bus is located within the motherboard and is the main highway for data. It connects the processor, chipset, DRAM, and graphics controller. The memory bus runs from the memory controller to the memory expansion slots on the motherboard.
Byte Eight bits of information. The byte is the fundamental unit of computer processing; almost all specifications and measures of computer performance are in bytes or multiples thereof, such as Kilobytes (KB) and Megabytes (MB). Don't confuse byte (capital "B") with bit (lower case "b"). Bytes are capitalized becase they represent 8 bits of information; they're the larger unit of measurement.
Cache A type of memory that holds recently accessed data, which is designed to speed up subsequent access to the same data. Cache is usually small and very fast memory.
Chipset A chip on a motherboard that controls the data flow between the processor and the other components of the system.
Clock rate The frequency at which a computer chip is running in one second. It determines the speed at which bits of information are processed or sent. The clock rate can be adjusted to process data at faster speeds.
CMOS Complimentary Metal-Oxide Semiconductor. The CMOS is the chip on the motherboard that stores information about the system's hardware settings, such as DRAM speed, timings, and voltage. You can alter the CMOS settings from the BIOS/CMOS setup.
Controller A chip that controls how data is stored, processed, and accessed.
CPU Central Processing Unit (processor) is the primary component of a computer that processes instructions. The CPU runs the operating system and applications.
Desktop Computer A computer designed to stay in a single location, not portable like a laptop computer.
DDR(X) Double data rate is a type of memory technology that can transfer data twice as fast as SDRAM. The number after "DDR" is the generation of technology under which the module was produced. DDR technology is not backwards compatible, so a system can use only one generation of memory. To find out which kind of memory your system is designed for, use the Crucial® Advisor™ tool or System Scanner tool.
DIMM Dual inline memory module. DIMMs are memory modules for desktop systems.
DRAM Dynamic Random Access Memory is a type of computer memory that stores each bit of data on a separate capacitor. This is the most common kind of computer memory.
Driver A software program that enables a specific hardware device to work with a computer's operating system.
Dual Channel Dual channel technology uses two identical memory controllers so that two DRAM modules can be accessed simultaneously, which decreases memory lag times between one command and the next. Dual channel technology is present on most modern systems, but in order for the technology to work, the two memory modules that are installed in a system must be identical.
ECC Error Correcting Code is a logic used on some DRAM chips to catch and correct memory errors.
ESD Electrostatic discharge is a burst of built up static electricity that can cause damage to electronic components. For this reason, we recommend wearing an antistatic wrist strap when dealing with memory and other components.
FAT The file allocation table tells the computer where every file is located and how it can be accessed.
File System A system that determines how data files are stored and accessed on a storage device.
Firmware A type of computer program that allows a piece of hardware to work.
Flash Memory A type of non-volatile data storage that's used in USB flash drives, digital camera flash cards, and solid state drives. Flash memory uses different technology from computer memory (DRAM).
Form Factor The physical size and shape of a hardware component.
Formatting A process to prepare a storage drive for use by configuring it with a file system.
FSB The Front Side Bus is located within the motherboard; the FSB is the main highway for data in your computer. It connects the processor, chipset, DRAM, and graphics controller. The FSB is described in terms of its width (in bits) and its speed (in megahertz).
Garbage collection A process that helps a solid state drive maintain optimal performance by freeing up memory sectors that are filled with data that has been deleted from the file. Garbage collection is part of the SSD and not dependent on the computer's operating system.
Gigabit An amount of memory equal to 1024 megabits (1,073,741,824 bits) of information. Abbreviated Gb.
Gigabyte An amount of memory equal to 1024 megabytes (1,073,741,824 bytes) of information. Abbreviated GB. Other common DRAM units of measurement are kilobytes, megabytes, gigabytes, and terabytes. Because bytes contain 8 bits of information, gigabytes are naturally larger than gigabits.
GPU Graphics Processing Units (video card) are a specialized electronic circuit that rapidly manipulates and alters computer memory to create images intended for display on a screen with high clarity, definition, and appearance.
HDD Hard Disk Drives are storage drives made up of magnetic spinning platters which rotate at high speeds and an actuating arm which reads and writes data.
Hardware The physical machinery and devices that make up a computer system.
Heat Spreaders A cover on a DRAM module that helps dissipate heat. Heat spreaders are usually made of aluminum and are used on some server modules and on Crucial Ballistix performance modules.
Hertz A hertz refers to one clock cycle, or one per second. Hertz are used to measure transfer speeds in computer systems. See also Megahertz.
Interface The means by which two independent systems communicate. For SSDs, the interface is a connector that plugs the solid state drive into the motherboard and power supply.
JEDEC Joint Electron Device Engineering Council is an organization that establishes industry standards for memory operation, features, and specifications.
KB Kilobyte is a unit of measure equal to 1,024 bytes.
LRDIMM Load-Reduced DIMM is memory technology that enables more DIMMS per channel and doubles the installed memory capacity of a module, allowing up to 35% greater memory bandwidth.
Laptop Computer Portable computer.
Latency Latency is the amount of time it takes for your system's memory to respond to a command. Generally speaking, the lower the delay (latency), the faster the device. However, when increasing speeds, the higher overall speed can be faster even though the latency is higher.
LBA Logical Block Addressing is a method for specifying locations on a computer storage drive.
LPM Link Power Management. A SATA feature that reduces power to a solid state drive when the computer is turned off.
MHz Megahertz is a measurement of clock cycles in millions of cycles per second. Used to show memory speeds, ex. 1333MHz or 1600MHz. See also Hertz.
Malware Software that is intended to damage or disable the data on a computer.
MB Megabyte is a unit of measure equal to 1,048,576 bytes.
Memory Bus Memory bus runs from the memory controller to the memory expansion slots on the motherboard. Memory bus speed can vary and is measured in megatransfers per second (MT/s).
Memory Controller The logic chip used to handle the data flow going to/from the memory. It can reside in the main chipset or in the CPU.
MLC Multi-Level Cell is flash memory architecture that has two bits of data stored in each memory cell, allowing four states of operation. This allows for greater memory capacity at lower cost than single-level cells.
Module A module is the actual memory component - it's what you take out of the packaging and install in your system. When you purchase a memory upgrade, it will come in the form of a memory module. DIMMs (desktop memory modules) and SODIMMs (laptop memory modules) are the most common types of memory modules.
Motherboard The main printed circuit board in a computer that carries the system buses. It is equipped with sockets to which all processors, memory modules, plug-in cards, daughterboards, or peripheral devices are connected.
mSATA Mini Serial Advanced Technology Attachment is an interface standard to connect very thin solid state drives to a motherboard for use in notebooks and ultrabooks.
MTBF Mean Time Between Failure is the time between one data failure and the next on a computer storage drive.
NAND NAND refers to flash memory, so think of it like your flash drive. When you pull the flash drive out of your computer, it retains any information that you stored on it. Flash memory (NAND) is what makes this happen. When you remove the power source, the flash memory retains its information. Micron is one of the largest NAND manufacturers in the world.
NQC Native Command Queuing is a feature that allows SATA drives to optimize the order in which read/write commands are executed, increasing overall SSD performance gains.
Notch Notches are cut outs that are located on the bottom of a memory module. Each memory type (SDRAM, DDR, DDR2, DDR3, and DDR4) has a unique notch location for DIMMs and SODIMMs in order to prevent the wrong type of memory from being installed in the system. Notches also help ensure that the memory module is installed correctly.
NTFS New technology File System is used in storage drives for Microsoft® Windows® operating systems.
OS The OS is the operating system that your computer runs on, such as a Windows or Mac OS.
Overclocking Running a chip at a higher clock speed than it was specified for. Oftentimes chips are capable of running faster than a manufacturer specifies, and thus can be safely overclocked. To overclock a chip, set it to either a higher bus speed, a higher multiplier, a higher voltage rate, or any combination thereof.
Partitioning Disk partitioning divides the space of a storage drive into separate data areas, known as partitions. Think of partitioning like a chest of drawers for your data. If your data is in a storage location, a drawer, then the partition is the wood that divides the drawers.
PATA Parallel Advanced Technology Attachment is an older interface standard that connects legacy HDDs, CD/DVD drives, and floppy disk drives to your computer's motherboard—think of it like an umbilical cord because it allows data to flow between the two. PATA technology has largely been superseded by SATA technology.
PC Personal Computer, typically used to indicate a non-Mac® computer.
PCB Printed Circuit Boards are made for connecting electronic components. In computer memory, it is the green circuit board that the black DRAM chips sit on. PCBs are made of non-conductive material and contain layers of circuitry that connect the various memory components to the system.
Program A set of instructions that a computer uses to perform a particular operation. Microsoft Word is a word processing program.
Peripheral Hardware devices used to put information into or get information out of a computer. A mouse, keyboard, and monitor are examples of peripherals.
QLC Quad-level cells are the newest technology deployment in flash memory architecture. QLC store four bits of data in each memory cell. QLC offers greater densities in a smaller footprint and is positioned as an attractive solution for read-centric applications
RAM Random Access Memory is volatile data storage for data being currently used. RAM is random access because the location of the stored information does not affect the access speed. The more RAM that's available, the more applications you can have running simultaneously without slowing your system down.
RAID Redundant Array of Independent Disks is a data storage device that combines two or more storage drives to work as one drive for better performance.
RDRAM Rambus Dynamic Random Access Memory is an alternative type of memory used in some older systems. Rambus technology uses a narrow 16-bit bus (Rambus channel) to transmit data at high speeds of up to 800MHz.
Read Refers to accessing a piece of data from memory or a storage drive.
RDIMMs Registered Dual Inline Memory Modules are types of DRAM with a register between the memory and the memory controller. The register holds the data for one clock cycle, increasing reliability.
ROM Read Only Memory contains the base instructions for starting up your computer. ROM is not user-replaceable.
S.M.A.R.T Self-Monitoring, Analysis, and Reporting Technology is a monitoring system for storage drives designed to detect and report on various indicators of reliability and use that data to anticipate and avoid system failures.
SATA Serial Advanced Technology Attachment. A type of interface that connects a storage drive to a motherboard.
SDRAM Synchronous Dynamic Random Access Memory transfers data in synchronization with the memory bus.
SLC Single-Level Cell is flash memory architecture that has one bit of data stored in each memory cell, allowing two stated of operation.
SODIMM Small Outline DIMM. Measuring at just half the length of a standard DIMM, SODIMMs are memory modules used in laptops.
Software General term for programs and the operating system for computers.
SPD Serial Presence Detect is a memory feature that stores information about the module on the module's EEPROM chip. The BIOS then uses this information at startup to establish the specifications of the memory module.
Speed There are two types of speed: frequency and bandwidth. Frequency refers to how many cycles the data can run per second, expressed in MHz per second. Bandwidth refers to how much data can go through a system, expressed as gigabytes (GB) per second. DRAM is measured in MHz and bandwidth. Often both will be shown in the form of DDR3-1333 PC3-10600 where the 1333 refers to the MHz speed and the 10600 the bandwidth in MB/s.
SSD Solid State Drives are flash-based data storage drives designed to function like traditional hard disk drives (HDDs) using NAND technology. Not only are they faster and more durable than traditional hard drives, they also offer faster boot times and they use less power. Unlike HDDs, SSDs have no moving parts so they are less prone to damage or component failure.
Storage Refers to a device on which you can permanently keep data.
Storage Drive Hardware such as an SSD or an HDD that stores software and data files.
Swapping When a computer system borrows memory on the storage drive because the random access memory is full. Swapping is also referred to as virtual memory.
Terabyte Unit of measure equal to 1,099,511,627,776 bytes, or 1,024 gigabytes.
Timings Timings refer to the latency of a given memory module. Standard memory will only list the CAS Latency (CL) timing, e.g. CL=8. Performance modules such as Ballistix list CL, tRCD, tRP and tRAS in the form of four numbers seperated by dashes, e.g. 8-8-8-24. Taken together, these four numbers represent a module's timings (like latency, the lower the number, the better the performance).
TLC Triple Level Cell is flash memory architecture that has three bits of data stored in each memory cell and is a solution that offers a good cost versus performance balance.
Tri-Channel An extension of Dual Channel technology that can be found in some DDR3 systems. Tri-channel uses three identical memory modules for interleaving, allowing for fewer lags in memory performance.
Trim A command that allows the operating system to inform a solid state drive which data blocks are no longer in use to be cleared and reused. This is the same as garbage collection, but initialed by the operating system.
UDIMMs Unbuffered Dual Inline Memory Modules are standard in PCs, laptops, and Macs.
USB Universal Serial Bus is the industry standard connection common in computers for connecting peripherals.
Virtual Memory Virtual memory is when your system borrows some of the hard drive's memory when all of its RAM is in use.
Virus Type of malicious software that, when executed, replicates itself by modifying other computer programs and inserting its own code.
Wear Leveling Wear Leveling ensures that all NAND cells on a flash-based device are used evenly, which prolongs the life of a memory card, flash drive, or SSD. How wear leveling works is that data is stored in a certain part of each cell and each cell has a limited life. When data is consistently accessed from the same cell (location), it gradually wears the cell out over time. Wear leveling technology allows data to be dispersed more evenly and thus avoid wearing the cells out.
Write Refers to how quickly a piece of data can be saved to a storage device (saving a document is an example of a write function).
XMP Extreme Memory Profile is an Intel standard for providing faster timings over the standard JEDEC SPD. Memory that supports XMP can be easily overclocked by enabling XMP in the CMOS/BIOS setup.

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