Memory Form Factors

The first fact you need to know when you order memory for a system is what type of memory module it uses. The original form of memory used in the IBM PC, XT, and AT models and other computers of the time (early to mid-1980s) was individual RAM chips, ranging in size from 16Kb to 1Mb. These chips were installed on the motherboard or add-on cards that plugged into expansion slots on the motherboard. Because memory chips are sized in bits, not bytes, it took multiple chips to reach a given capacity. Some add-on cards for memory upgrades were so large that they ran the full length of the case and sometimes contained two layers of chips. Starting in the late 1980s, memory modules (small printed circuit boards [PCBs] with multiple ...

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