Here's our Hardware Tip for.. February 19, 1999
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RAM (Random Access Memory)
RAM (random-access memory) is where the CPU stores programs and data it is currently using. RAM is measured in units called bytes. Modern PCs have many millions of bytes of RAM, so RAM is measured in units called Megabytes. An average PC will usually have anywhere from 8 to 64 Mbs of RAM, although it can easily be more or less. RAM has been packaged in many different ways over the years. The two most current (and common) packages are called SIMMs (single inline memory module) and DIMMs (dual inline memory module).

There are many different sizes of SIMMs and DIMMs. The two most common sizes of SIMMs are 30-pin and 72-pin. It's easy to tell the difference between them, as the 72-pin SIMM is much larger than the 30-pin SIMM. 72-pin SIMMs are more modern and are designed to hold more RAM than 30-pin SIMMs. 72-pin SIMMs can also transfer information to and from the CPU faster than 30-pin SIMMs. There are also two different sizes of DIMMs used by PCs: a 168-pin DIMM and a 72-pin SO DIMM. The SO DIMM is very small, and its small size makes it very popular in laptops. Only the 168-pin DIMMs are commonly used in desktop PCs.

For more information on the types and configurations of memory modules available today, you might want to check out two of the biggest memory manufacturers on the web, Micron and Kingston.