    |
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
Access Time - Typically expressed in nanoseconds (ns), for RAM to complete one access. Access Time is composed of address setup time and latency (the time it takes to initiate a Request for data and prepare access).
AMD™ - (Advanced Micro Devices) - Supplier of Intel-compatible CPUs for personal computers and flash memory. See Athlon, Duron, K6-2.
ANSI - (American National Standards Institute) - The U.S. organization responsible for setting information technology standards.
Apple™ - Apple's PowerPC-based Macintosh, iMAC, PowerMAC, etc. Personal Computers are the primary standard competing with IBM-compatible PCs.
ASCII - (American Standard Code for Information Interchange) - A method of encoding text into binary values. ASCII contains 256 combinations of 7-bit or 8-bit binary numbers to represent all possible keystrokes.
Athlon™ - Athlon and Athlon XP are versions of AMD's Windows-/Intel-compatible CPU targeted for computation-intensive requirements on high-performance desktop systems. Also known as the K7. Athlon and Athlon XP chip sets mostly DDR but there is also SDRAM support.
Bandwidth - The rate at which data can be moved or accessed. Typically expressed in bits per second, bytes per second, or words per second.
BGA - (Ball Grid Array) - A chip package employing solder balls on the underside, instead of pins on the sides, for mounting. BGA allows for a reduction in die package size, better heat dissipation, and greater module densities. Common types include fBGA, micro BGA.
Bank - See memory bank.
Binary - A numbering system using combinations of 0 and 1 to represent data. Also known as Base 2.
BIOS - (Basic Input/Output System) - Startup routine which prepares the computer for operation. The BIOS sometimes dictates the amount of memory which can be addressed.
Bit - The smallest unit of information. A bit is 1 or 0.
BSB - (Backside Bus) The bus which runs between the CPU and L2 cache.
Buffered Memory - Memory modules which contain buffers. A buffered module allows systems to utilize denser modules by re-driving the system signals through a larger number of memory chips than a typical system can support. Buffered and unbuffered memory cannot be mixed in the sane system. The selection of buffered or un-buffered memory is usually dictated by the chip set.
Burst - see Burst Mode.
Burst Mode - A method to increase the bandwidth of a memory subsystem, typically by returning the contents of multiple consecutive addresses from a single CPU address request.
Bus - A data path in a computer.
Bus Cycle - A single transaction between CPU and main memory.
Byte - Eight bits of information. The byte is the fundamental unit of computer processing; most specifications and measures of computer performance are in bytes or multiples thereof. See Kilobytes and Megabytes.
Cache Memory - A small amount (normally less than 1MB) of high-speed memory residing on or close to, or on, the CPU. Cache memory supplies the processor with the most frequently used data and instructions. Level 1 cache (primary cache) and Level 2 cache (secondary cache) refer to the degree of proximity to the CPU. (Level 1 is closest.)
Capacitor (cap) -A device built onto most modules, usually one or more per IC, to limit the voltage and smooth out the rate at which voltage increases or decreases. Units of capacitance are typically mf (micro-farads) or pf (pico-farads).
CAS - (Column Address Strobe) - Refers to the latching of the column address in a DRAM's row-column matrix.
CAS Latency - The delay between an initial CAS signal and the arrival of the first data, typically expressed as a multiple of the system clock (CLK). For example, CAS Latency 2 (CL2 or /CL2) indicates data arrives on the second CLK signal after CAS is generated. Subsequent data can be received on each CLK signal.
Celeron™ - An Intel processor targeted at the "value" segment of the PC market.
Chipset - Chips which support memory interface and other system functions/interfaces for the CPU.
CLK - Abbreviation for Clock. Usually refers the main system clock which also drives the CPU.
CompactFlash - A small, lightweight form factor for removable storage cards.
Coppermine™ -A version of Intel Pentium III released in 1999.
CPU - (Central Processing Unit) - The computer chip with primary responsibility for executing commands in an electronic system. The CPU is also known as a processor or microprocessor.
DDR -Double-Data Rate - Refers to synchronous memory architectures which recognize data on both rising and falling edges of the CLK signal.
DDR-200 - Refers to 200Mbps synchronous DRAM systems (which can be thought of as a PC-100 architecture recognizing data on both clock edges).
DDR-266 - Refers to 200Mbps synchronous DRAM systems (which can be thought of as a PC-133 architecture recognizing data on both clock edges).
DDR-333 - Refers to 200Mbps synchronous DRAM systems (which can be thought of as a PC-166 architecture recognizing data on both clock edges). DDR-333 is targeted at point-to-point systems instead of modules.
DDR SDRAM - (Double Data Rate Synchronous Dynamic Random Access Memory) - Data is read on both rising and falling edges of the computer clock, thereby delivering twice the bandwidth of standard SDRAM. With DDR SDRAM, memory speed doubles while using the same clock frequency.
DIMM - (Dual In-line Memory Module) - Refers to the memory module PCB with leads on either side which are electrically independent. This is a way to increase the density of memory which can addressed from a given size of connector. (see also SIMM.)
DIP - (Dual In-line Package) - DIPs has two rows of pins which are used to mount though holes in PCBs. DRAM ICs were once only packaged in DIPs but today are only available in surface-mount packages such as SOJ, TSOP and BGA.
DRAM - (Dynamic Random-Access Memory) - As opposed to SRAM, DRAM data cells, to increase density, only hold data for a short time. To retain data, DRAM cells must be refreshed periodically, usually by the memory controller or chip set, typically 4K or 8K times per second. If the cell is not refreshed, the data disappears.
Dual-Banked - A memory module or memory system having two banks.
Duron -Version if AMD's Windows-/Intel-compatible CPU targeted for desktop personal productivity, education and entertainment applications. AMD Mobile Duron is similar while offering longer battery life for Notebooks.
ECC - (Error Correction Code) - Also know as Haming code. A method for checking the integrity of data in DRAM. ECC can correct single-bit errors and detect multiple-bit errors.
EDO - (Extended Data Out) - A DRAM technology which shortens the read cycle between memory and CPU. On computers supporting it, EDO improves memory performance over FPM.
EEPROM - (Electrically Erasable Programmable Read-Only Memory) - A non-volatile memory technology which can be erased and reprogrammed electrically, often down to the byte level, within the computer or externally.
EIA - (Electronics Industry Association) A national trade organization which includes a broad spectrum of U.S. manufacturers. The 2,300 member companies range from small electronic components and services to complex systems used by defense, space and industry, including a full range of consumer electronic products. (http://www.eia.org/)
EPROM - (Erasable Programmable Read-Only Memory) - A programmable and reusable chip that retains content until erasure under ultraviolet light. EPROMs are programmed outside the system in which they are used.
fBGA - Fine-pitch Ball Grid Array. This is the initial BGA version utilized by Micron for their DRAMs.
FPM - (Fast-Page Mode) - One of the first methodologies to increase DRAM, fast-page mode's advantage over previous page mode memory technologies was faster access to data in the same row.
Flash Memory - A version of EEPROM offering increased density, typically re-writable in blocks or pages.
Form Factor - The size, shape and other specifications used to describe hardware. Examples of memory module form factors are: SIMM, DIMM, SODIMM, 30-pin, 72-pin, 144-pin and 168-pin.
FSB - (Front-side bus) The bus which runs between the CPU and main DRAM memory.
Gigabit - Roughly 1 billion (1,073,741,824) bits, or exactly 1,024 x 1,024 x 1,024 bits.
Gigabyte - Roughly 1 billion (1,073,741,824) bytes, or exactly 1,024-cubed bytes.
GHz - Roughly 1 billion Hertz, or 1 billion cycles per second.
Heat Spreader - A sheath which covers an electronic device to dissipate heat.
Heat Sink - A component attached to an IC to dissipates heat. Most recent CPUs require heat sinks to operate safely.
Hub Architecture -Intel I/O architecture developed to improve performance over traditional northbridge/southbridge technology.
IBM - (International Business Machines) Developed the first commercially-viable PC product around 1982 using on Intel CPUs and DOS operating system licensed from Microsoft. Today, PCs are either IBM- or Apple-compatible.
IC - (Integrated Circuit) - An electronic circuit on a semiconductor chip. The circuit includes components and connectors. A semiconductor chip is usually molded in a plastic or ceramic case and has external connector pins.
IEEE - (Institute for Electrical and Electronics Engineers) the leading global professional organization in electrotechnology, information technologies and related sciences. (www.ieee.org)
Intel - Developer of CPU initially chosen for IBM PCs. Today they are the leading supplier of CPUs in the world.
Interleaving - Techniques for increasing memory speed. By successively accessing alternate memory banks, memory bandwidth can be increased.
I/O - Abbreviation for Input/Output.
Itanium™ - Intel CPU offering high levels of floating-point performance for complex, numerical-intensive applications.
JEDEC (http://www.jedec.org/) - (Joint Electron Device Engineering Council) - An Electronic Industries Alliance (EIA) body that sets semiconductor engineering standards.
KHz - Abbreviation for thousands of Hertz, or thousand cycles per second.
Kilobit - Approximately one thousand bits, or exactly 1 bit x 210 (1,024) bits.
Kilobyte - Approximately one thousand bytes, or exactly 1 byte x 210 (1,024) bytes.
Level 1 Cache - (L1) - Also L1 Cache, a small amount of high-speed memory which resides on or very close to the processor. L1 Cache supplies the processor with the most frequently accessed data and instructions.
Level 2 Cache - (L2) - L2 Cache, a small amount of high-speed memory which resides close to the CPU, usually on the motherboard. L2 Cache supplies the processor with a next tier most frequently requested data and instructions.
Logic Board - See Motherboard.
Macintosh - Model name for Apple PCs, first introduced in 1984.
MCH - (Memory Controller Hub) The portion of Intel chipset supporting memory interfaces. Different versions support SDRAM, DDR or Rambus.
Megabit - Approximately one million (1,048,576) bits, or exactly 1 bit x 1,024 bits.
Megabyte - Approximately one million (1,048,576) bytes, or exactly 1 byte x 1,024 bytes.
Memory - A computer's storage area. Typically refers to DRAM.
Memory Bank - A logical division of memory in a computer, dictated by the CPU. For example, a 32-bit CPU requires memory banks that provide 32 bits of information at a time. A bank can consist of one or more memory modules. For example, two 32-bit SIMM modules would be needed form one bank in a computer with a 64-bit CPU. Also, a memory module can be divided into one or more banks. For example, one 64-bit DIMM module consisting of 16 8-bit wide memory IC's would be logically divided into two banks in a computer with a 64-bit CPU.
Memory Bus - The bus that runs from the CPU to the memory array and/or memory module slots.
Mezzanine Card - Refers to a style of memory module often utilized in PowerPC-based systems. Uses a different form factor than mainstream memory modules
MHz - Abbreviation for 1 million Hertz, or million cycles per second.
Micro BGA - (µBGA) - Chip packaging technique which allows for a reduction in package size and footprint, improved heat dissipation and greater module densities.
Micro-Second - (µs) 1 times 10 to the minus-6 seconds.
Milli-Second - (ms) 1 times 10 to the minus-3 seconds.
Mini-PCI - (Miniature Peripheral Component Interconnect) Expansion card technology provides an industry standard for integrating communications devices into small form factor products. Targeted for mobile applications but uses standard 32-bit PCI interface and PCI/BIOS interface.
Motherboard - A computer's main board which in most cases holds all CPU, memory, and I/O functions and/or has expansion slots. Also referred to as a logic board or computer board.
MPT - (Memory Protocol Transfer) An Intel-supported function to translate SDRAM signaling to RDRAM signaling.
Nanosecond - (ns) - One billionth of a second (1 times 10 to the power of negative-9). Memory data access times are currently expressed in nanoseconds.
Nibble - One-half an 8-bit byte, or 4 bits.
Page Mode - see FPM
Parity - Adds a single bit to each byte of data to detect errors in the other 8 bits. Parity can be implemented as "even" or "odd."
PCB - (Printed Circuit Board) - Boards made of fiberglass, typically green in color, with multiple layers of electrical traces.
PC - Personal Computer. Sometimes refers an IBM-compatible and/or Windows-/Intel-compatible personal computer or to distinguish from an Apple machine.
PC-100 - 100MHz synchronous memory bus.
PC-133 - 133MHz synchronous memory bus.
PC-166 - 166MHz synchronous memory bus. Sometimes referred to as PC-167.
PC2100 - Indicates 2,100MBytes per second, or 2.1GBytes per second. This is the bandwidth available from a DDR-266 memory system.
PC2600 - Indicates 2,600MBytes per second, or 2.6GBytes per second. This is the bandwidth available from a DDR-333 memory system.
PC-66 - 66MHz synchronous memory bus.
PC Card - Standard defines a 68-pin interface between the peripheral card and the socket into which it is inserted. There are three standard PC Card form factors, called Type I, Type II and Type III. All PC Cards measure the same length and width, differing only in thickness. Sometimes used as a shorthand for PCMCIA.
PCI - (Peripheral Component Interconnect) - A peripheral bus that can send 32 or 64 bits of data simultaneously. PCI offers plug-and-play capability.
PCMCIA -(Personal Computer Memory Card International Association) an international standards body and trade association with over 200 member companies founded in 1989 to establish standards for Integrated Circuit cards and promote interchangeability among mobile computers where ruggedness, low power, and small size were critical.
Pentium III™ - Third generation of Intel's Pentium processor family.
Pentium IV™- Fourth generation of Intel's Pentium processor family. Intel initially intended Pentium IV to only support Rambus memory but chipsets to support DDR SDRAM were released late-2001.
Pico-Second (ps) - 1 times 10 to the minus-12 seconds. Or 1/1000 of a nanosecond.
Pipeline Burst Cache - Cache that reduces wait states and accelerates memory access by using pipelining and bursting functions.
Pipelining - A technique in which memory loads the requested memory contents into a small cache composed of SRAM, then immediately begins fetching the next memory contents. This creates a two-stage pipeline, where data is read from or written to SRAM in one stage, and data is read from or written to memory in the other stage.
PLCC - Plastic leaded chip carrier. A type of IC package.
PLL - Phase-Locked Loop. A PLL generates a base frequency from which synchronous system clocks are synchronized.
PowerPC - A CPU architecture developed by Motorola and IBM to compete with Intel. Apple computers use PowerPC CPUs. Recent versions of PowerPC utilize SDRAM.
Proprietary Memory - Memory custom designed for a specific application.
RAM - (Random-Access Memory) - Random means data from any address within the memory array can be accessed. See also Memory.
Rambus - Proprietary memory design developed and licensed by Rambus, Inc. Rambus memory can offer higher bandwidth in some applications but has also been found to be significantly more expensive than SDRAM and DDR alternatives.
RAS - (Row Address Strobe) - Refers to the latching of the row address in a DRAM's row-column matrix.
RDRAM - Acronym for Rambus DRAM.
Refresh - The signal sent to recharge the capacitors in a DRAM to maintains each cell's data. Various DRAM components require different refresh rates.
Refresh Rate - The frequency with which a DRAM component must be refreshed. Common refresh rates to day are 2K, 4K and 8K.
Register - A type of IC added to registered memory modules to hold the data ready until the next system clock signal arrives.
Registered Memory - SDRAM memory module which contains registers on the module. A registered module allows systems to utilize denser modules by re-driving the system signals through a larger number of memory chips than a typical system could support. Registered and unbuffered memory cannot be mixed. The chipset dictates which type of memory is required.
RIMM™ - The trademarked name for a Direct Rambus memory module.
RIMM Connector - A socket for a RIMM.
SDRAM - (Synchronous DRAM) - A DRAM technology using the system clock to synchronize signal input and output on a memory chip. Synchronous DRAM offers improved memory performance over EDO.
Self-Refresh - A type of DRAM which can refresh itself, independent of the CPU or external refresh circuitry.
Serial Presence Detect - (SPD) - An EEPROM chip on a memory module containing information about size and speed, as well as other specifications and manufacturer idenitifcation.
SIA - (Semiconductor Industry Association, www.semichips.org) A trade association representing the U.S. microchip industry. SIA comprises 90 percent of U.S. semiconductor production. The SIA provides a forum for domestic semiconductor companies to work collectively to advance the U.S. chip industry.
SIMM - (Single In-line Memory Module) - A memory module on which the metal leads on either side of the board are electrically connected.
SMART CARD - An electronic device, similar in size to a credit card, which an embedded IC.
SO DIMM - (Small-Outline Dual In-line Memory Module) - A reduced form factor version of a standard DIMM. SO DIMMS are the memory module of choice in most Notebooks.
SO-RIMM™ - The trademarked name for a Direct Rambus memory module in notebook computers. SO-RIMM™s provide memory bandwidth comparable to desktop memory configurations.
SOJ - (Small-Outline J-lead) - A common package for surface-mount DRAMs. An SOJ is rectangular with J-shaped leads on the two long sides.
Stack - The result of mounting two DRAM IC's, one on top of the other. A stack, or stacked IC, is then mounted on the memory module PCB in single IC footprint or pad. Stacking is a common method of increasing the amount of memory which fits on a given module PCB.
Static RAM - (SRAM) - A memory chip that requires power to retain content. SRAM is faster than DRAM but more expensive and bulky. A typical use for SRAM is cache memory.
Storage - A data-holding device, such as a hard disk or CD-ROM.
Swapping - Using space in the hard drive as system memory when the RAM space is full. A system which spends a significant portion of its bandwidth swapping is said to be "thrashing."
System Board - See Motherboard.
Thrashing - A system which is thrashing is degrading its overall performance by spending parts of its bandwidth swapping data back and forth between RAM and its hard disk.
Timna - A later version of Intel's Celeron processor with integrated video and MCH. Timna was introduced supporting Rambus memory but also supports DDR by virtue of an MPT.
TSOP - (Thin Small-Outline Package) - A common package for surface-mount DRAMs. The package is rectangular with gull-wing shaped leads on the two long sides. A 54-pin TSOP is common for SDRAM while a 66-pin version is standard for DDR SDRAMs.
Tualatin - A .13 micron version of the Intel Pentium III with 512k of L2 cache.
Unbuffered Memory - Memory modules which do not contain buffers or registers on the module. Unbuffered modules cannot be mixed with buffered or registered modules in the same system. The selection of un-buffered or buffered memory (or registered memory in synchronous systems) is usually dictated by the chip set.
Validation - Typically refers to a test and/or process performed to confirm a specific memory module will function correctly in a system using a particular CPU and chip set combination.
Via - 1) A Taiwanese company which designs and manufactures chip sets for Intel and other CPUs.; 2) A term used to refer to the traces etched on or embedded in PCBs.
Virtual Memory - Refers to a system process where space on the hard disk treated as part of main DRAM memory. When RAM is full, the computer swaps data between DRAM and the hard disk, as needed. See Swapping.
VRAM - (Video Random-Access Memory) - Dual-port memory typically found only on a video or graphics card. One port is dedicated to the CRT and refreshes and updates the image. The second port is for the CPU or graphics controller to change the image data in memory.
Wait State - When the processor and memory utilize different clock speeds, which is common in modern systems, the processor sometimes has to "wait" for instructions and/or data to be returned from memory.
Word - Historically indicated the concatenation of two 8-bit bytes into a 16-bit word. In recent usage it can also refer to whatever number of bits is required to execute a CPU instruction (commonly 32 or 64 bits) .
Xeon™ - An Intel processor targeted to server applications.
©2003-2004 Quadrant Components, Inc. All rights reserved.
|