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ACCESS TIME:
The average time (in nanoseconds) for RAM to complete 1 access. Access Time is composed of address setup time and latency (the time it takes to initiate a request for data and prepare access)
AGP:
(Accelerated Graphics Port) An Intel developed interface that enables high-speed graphics. Graphics data moves between the PC’s graphics controller and computer memory directly, instead of being cached in video memory.
BANDWIDTH:
The amount of data moved on electronic lines, such as a bus, per second, bytes per second, or cycles per second (Hertz)
BGA:
(Ball Grid Array) A chip package having solder balls on the underside for mounting. BGA allows for a reduction in die package size, better heat dissipation, and greater module densities.
BIOS:
(Basic Input-Output System) Startup routines that prepare the computer for operation.
BUFFERED MEMORY:
A buffered module is very similar to a registered module. Buffers re-drive the signals through the memory chips and allows for the module to be built with more chips. Buffered and unbuffered memory chips cannot be mixed. The design of the computer memory controller dictates whether memory must be buffered or
unbuffered.
BUS:
A data path in a computer, consisting of various parallel wires to which the CPU, memory, and all input/output devices are connected
CACHE MEMORY:
A small amount (normally less than 1MB) of high-speed memory residing on or close to the CPU. Cache memory supplies the processor with the most frequently requested data and instructions. Level 1 cache (primary cache) is the cache closest to the processor. Level 2 cache (secondary cache) is the cache second closest to the processor and is usually on the motherboard.
CAS LATENCY:
CAS Latency (Column Address Strobe). The ratio between column access time and clock cycle time. CAS Latency 2 (CL2) offers a slight performance increase over CAS Latency 3 (CL3).
COMPACT FLASH:
A small, lightweight form factor for removable storage cards. CompactFlash cards are durable, operate at low voltages, and retain data when power is off. Uses include digital cameras, cell phones, printers, handheld computers, pagers, and audio recorders.
CPU:
(Central Processing Unit). The computer chip that has primary responsibility for interpreting commands and running programs. The CPU is also known as the processor or microprocessor
DDR:
DDR (Double Data Rate) is twice as fast as SDRAM doubling the data rate transfer of SDRAM. These will only work in motherboards specifically designed to use DDR.
DIMM:
(Dual in-line memory module) A printed circuit board with gold contacts and memory devices. A DIMM is similar to a SIMM, but with this primary difference: unlike the metal leads on either side of a SIMM, which are tied together electrically, the leads on either side of a DIMM are electrically independent.
DIRECT RAMBUS:
RAMBUS also known as RIMM™, is Rambus technologies third generation, which offers a completely new DRAM architecture for high-performance PC’s. Data transfers at speeds up to 800MHz over a narrow 16-bit channel, compared to current SDRAM, which operates at 100MHz on a wide 64-bit bus.
DRAM:
(Dynamic Random-Access Memory). The most common form of RAM, DRAM can hold data for only a short time. To retain data, DRAM must be refreshed periodically. If the cell is not refreshed, the data will disappear.
DUAL BANKED:
A memory module having two banks.
ECC:
(Error Correction Code) A method of checking the integrity of data in DRAM. ECC provides more elaborate error detection than parity. ECC can detect multiple-bit errors and can locate and correct single-bit errors.
EDO:
(Extended Data-Out) A DRAM technology that shortens the read cycle between memory and CPU. On computers that support it, EDO memory allows a CPU to access memory 10 to 20 percent faster than comparable fast-page mode memory.
EEPROM:
(Electrically Erasable Programmable Read-Only Memory). A memory chip that retains data content after power has been removed. EEPROM can be erased and reprogrammed within the computer or externally.
EPROM:
(Erasable Programmable Read-Only Memory) – A programmable and reusable chip that retains content until erasure under ultra violet light. Special equipment erases and reprograms EPROMs.
FPM:
(Fast Page Mode). An early form of DRAM, fast-page mode’s advantage over previous page mode memory technology was faster access to data in the same row.
FSB:
(Front Side Bus). The data path that runs between the CPU and the main memory (RAM)
INTERLEAVING:
Techniques for increasing memory speed. For example, with separate memory banks for odd and even addresses, the next byte of memory can be accessed while the current byte refreshes.
LOGIC BOARD:
See Motherboard
MEMORY:
A computers random-access memory. Memory temporarily holds data, and instructions for the CPU. See RAM
MEMORY BANK:
A logical unit of memory in a computer, the size of which the CPU determines. 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.
MEMORY BUS:
The bus that runs from the CPU to the memory expansion slots.
MICRO BGA:
BGA chip packaging technique allows for a reduction in die package size, improved heat dissipation, and greater module densities.
MOTHERBOARD:
Also known as the logic board, main board, or computer board, the motherboard is the computer’s main board and in most cases holds all CPU, memory, and I/O functions or has expansion slots for them.
NANOSECOND:
(ns)- One billionth of a second. Memory data access times are in nanoseconds. For example, memory access times for typical 30 and 72 pin SIMM modules range from 60 to 100 nanoseconds.
PARITY:
Data integrity checking that adds a single bit to each byte of data. The parity bit is used to detect errors in the other 8 bits.
PCB:
(Printed Circuit Board). Generally flat, multi-layer boards made of fiberglass with electrical traces. The surface and sublayers use copper traces to provide electrical connections for chips and other components. Examples of PCB’s include: mother-boards, SIMMs, and credit card memory.
PC CARD:
(PCMCIA: Personal Computer Memory Card International Association). A standard that allows interchangeability of various computing components on the same connector. The PCMCIA standard supports input-output devices, including memory, fax/modem. SCSI, and networking products.
PCI:
(Peripheral Component Interconnect). A peripheral bus than can send 32 or 64 bits of data simultaneously. PCI offers plug-and-play capability
RAM:
(Random Access Memory). A memory cell configuration that holds data for processing by a central processing unit (CPU). Random means the CPU can retrieve data from any address within RAM. See also Memory
RAMBUS:
(1) Rambus, Inc. develops and licenses high-performance memory logic and circuit design technology and provides licensees with product design, layout, and testing information. (2) Direct Rambus is high-speed memory technology that uses a narrow 16-bit bus (rambus channel) to transmit data at speeds up to 800MHz.
REFRESH RATE:
The number of DRAM component rows that must be refreshed. Three common refresh rates are 2K, 4K and 8K
REGISTERED MEMORY
The term registered refers to how the memory module processes signals. Registered modules contain a register that delays all information transferred to the module by 1 clock cycle. This type of memory is primarily used in servers and was designed for modules with 32 or more chips on them to help ensure that data is properly handled.
RIMM™:
The trademark name for a Direct Rambus memory module. A RIMM™ conforms to the DIMM form factor and transfers data 16 bits at a time.
SDRAM:
(Synchronous DRAM). A DRAM technology that uses a clock to synchronize signal input and output on a memory chip. The clock is coordinated with the CPU clock so the timing of the memory chips and the timing of the CPU are in synch. Synchronous DRAM saves time in executing commands and transmitting data, thereby increasing the overall performance of the computer. SDRAM allows the CPU to access memory approximately 25 percent faster than EDO memory.
SERIAL PRESENCE DETECT:
An EEPROM chip that contains information about size and speed, as well as other specifications and manufacturer information of a memory module.
SGRAM:
(Synchronous Graphics Random-Access Memory). Video memory that includes graphics-specific read/write features. SGRAM allows data to be retrieved and modified in blocks instead of individually. Blocking reduces the number of reads and writes the memory must perform and increases the performance of the graphics controller.
SIMM:
SIMM (Single in-line memory module) is a printed circuit board having memory devices and gold or tin/lead contacts. A SIMM plugs into a computer memory expansion socket. SIMMs offer two main advantages: ease of installation and minimal consumption of board surface. A vertically mounted SIMM requires only a fraction of the space required by a horizontally mounted DRAM. A SIMM may have as few as 30 pins or as many as 200 pins. On a SIMM, the metal leads on either side of the board are electrically tied together.
SO DIMM:
(Small-Outline Dual in-line Memory Module) An enhanced version of a standard DIMM. A 72 pin small-outline DIMM is about half the length of a standard 72 pin SIMM. Standard sizes are 72 pin or 144 pin.
SWAPPING:
Using part of the hard drive as memory when RAM is full. See Virtual Memory.
UNBUFFERED MEMORY:
Memory that does not contain buffers or registers located on the module. Instead, these devices are located on the motherboard.
USB:
(Universal Serial Bus), is a computer standard designed for connecting peripherals to your PC. Currently, the USB Specification, Revision 2.0, covers three speeds 480 Mbps, 12 Mbps, and 1.5 Mbps. The term "Hi-Speed USB" refer to just the 480 Mbps portion of the USB Specification. We now use he term "USB" to refer to the 12Mbps and 1.5Mbps speeds.
VIRTUAL MEMORY:
Simulated memory. When RAM is full, the computer swaps data to the hard disk and back as needed. See swapping.
VRAM:
(Video Random-Access Memory). Dual-ported (two separate data ports) memory typically 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 and changes the image data in memory.
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