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Random Access Memory Random Access Memory (RAM) is considered temporary, or volatile memory. The contents of RAM are lost when the computer power is turned off. RAM chips on the computer hold the data and programs that the microprocessor is processing. In other words, RAM is memory that stores frequently used data for rapid retrieval by the processor. The more RAM a computer has, the more capacity the computer has to hold and process large programs and files. The amount and type of memory in the system can make a big difference in the system performance. Some programs have more memory requirements than others. Typically a computer running Windows 95, 98, or ME would have 64 MB installed. It is common to find systems with 128 MB or 256 MB of RAM, especially if they are running newer operating systems such as Windows 2000 or other network operating systems. There are two classes of RAM that are commonly used today. These are Static RAM (SRAM) and Dynamic RAM (DRAM).
RAM can be installed on the motherboard, either as a permanent fixture, or in the form of small chips, referred to as Dual Inline Package (DIPs). RAM is usually on small plug-in boards such as Single Inline Memory Modules (SIMMs) or Dual Inline Memory Modules (DIMMs). SIMMs and DIMMs are removable cards that can be replaced with larger or smaller increments of memory. Although having more memory installed on the computer is a good thing, most system boards have limitations on the amount and type of RAM that can be added or supported. Some systems may require that only SIMMs be used, while others may require that SIMMs be installed in matched sets of two or four modules at a time. Additionally, some systems use only RAM with parity (built-in error checking) while others use non-parity RAM (having no error checking capability).
Identifying SIMMs and DIMMs A DIMM plugs into the system's memory bank using a 168-pin
connector. The pins establish a connection with the system bus,
creating an electronic path through which data can flow between the
memory chip and other system components. A single 168-pin DIMM
supports 64-bit (non-parity) and 72-bit (parity) data flow. This
configuration is now being used in the latest generation of 64-bit
systems. Recall that parity refers to error checking capability built
into the RAM chip to ensure data integrity. An important feature is
that the pins on a DIMM board are not connected side to side (as with
SIMMs) forming two sets of contacts.
With most technologies, newer or more specialized forms of RAM are put out into the market all the time. Here are some examples that are of particular interest:
Most other types of RAM such as EDO RAM and FPM RAM are too slow
for today's computing standards and are no longer used in new
computers. Table
Cache Memory
L1 cache is faster than L2 because it is located within the CPU and runs at same speed as the CPU. It is the first place the CPU looks for its data. If data is not found in L1 cache, the search will then continue with L2 cache, and then on to main memory (or DIMM). L1 and L2 cache is made of SRAM chips. However, some systems use the COAST modules. COAST modules are used to provide cache memory on many Pentium-based systems. A COAST module essentially resembles a SIMM, except that it is taller and has a different connector. Additionally, it is noted for its reliability and speed because it uses the so-called pipeline-burst cache, which is significantly faster than SRAM cache. Some systems offer both SRAM sockets and a COAST module socket.
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gives a summary of useful information on
different types of RAM.
