MEMORY Terminology

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BE PATIENT, I'll add more terms as time and knowledge allows.

BIOS

Basic Input/Output System - Some consider it as memory because it has its own chip, and it contains the information necessary to do the POSTs, and it is accessable immediately. If it is memory, it is "non-volatile" memory, and is used each time you boot your system. I see it more as a special "storage" that is the program for booting PCs. The method used in DOS to communicate with any device on the system such as disks, keyboard, monitor, etc. Directs only system hardware, not network hardware.

CD (CD-ROM)

Compact Disk - Read Only Memory. Not really memory! But, a secondary, long term storage device; however, some purists insist it can be memory. Silly - it has access times slower than hard disk. Memory has access time of "nanoseconds". It requires a CD-ROM drive on the computer. Some writers consider this as a form of memory. I do not, so it will be discussed in "Storage Devices".

CACHE

A cache is a block of memory that holds frequently used data or data that is waiting for another process to use it. Cache is usually located between the CPU and RAM. It is often divided into internal (in your CPU) and external (on the motherboard between RAM and the CPU).

    Various types of "cache" are:

  1. Processor Cache
  2. Disk Cache
  3. Client-Server Cache
  4. Remote Cache

Cache is most often on chips that look similar to this:

but may be larger and have more pins. Cache is normally between the "microprocessor" and RAM. It has faster access than RAM, and is usually reloaded from RAM while the CPU is processing information just retrieved from RAM.

CMOS

Complementary Metal Oxide Semiconductor. This is the storage for your basic system configuration used at boot time. It describes the hardware devices to your system.

DMA

Direct Memory Access. A DMA controller is used to relieve the host microprocessor of overhead work. It performs the function of moving blocks of memory around inside the computer. This means it may do things like moving data from a hard disk through the disk controller into the PC's main memory. Speeds up the system.

DRAM

DYNAMIC RAM. This is your normal RAM component. Your SIMM chips will normally contain several DRAM chips embedded on the SIMM chip.

EDO RAM

Extended Data Out

EPROM

Erasable Programmable Read Only Memory

EEPROM

Electronically Erasable Programmable ROM.

FLASH Memory

Flash Memory Characteristics:

  1. Non-volatile Semi-Conductor Memory.
  2. Reads at the speed of DRAM (200ns), writes at speed of Disk (10ms).
  3. Technology is high density and low cost.
  4. Used for BIOS (updating by owner).
  5. Used like as a hard disk.
  6. Usually on a "flash card" - like a PCMCIA card. It is PCMCIA 2.0/ExCA compatible.

PROM

Programmable Read Only Memory.

RAM

Random Access Memory. This is the area set aside for loading programs and data. RAM is what you normally think of if you are referring to your PC's memory.

ROM

Read Only Memory. Normally used for BIOS, CMOS, EPROMs, and EEPROMs. Some ROM can be rewritten by applying a "higher" than normal electrical voltage (controlled of course) and some are erasable by ultraviolet light beamed through "windows" on the chip.

SIMM

Single-In-Line Memory Module

Note that SIMM chips come in 30, 72, 168, and probably other versions. SIMM chips are usually RAM and contain DRAM chips on the module.

SIPP

Single-In-Line Pin Package

I'll get photos of this and simms soon. JS.

SRAM

Static Random Access Memory. A form of RAM that requires fewer "refresh" cycles than DRAM. It is faster than DRAM, but more expensive to manufacture. It is used for "cache" memory located between the main RAM (DRAM) and the CPU.

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