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CompTIA A+ Certification All-in-One Exam Guide

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Figure 4-14 A motherboard showing four RAM slots. By populating the

same-colored slots with identical RAM, you can run in dual-channel mode.

SIM I’ve got a great Chapter 4 Challenge! sim on calculating RAM speeds

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DDR2

DDR2 is DDR RAM with some improvements in its electrical characteristics,

enabling it to run even faster than DDR while using less power. The big

speed increase from DDR2 comes by clock doubling the input/output circuits

on the chips. This does not speed up the core RAM—the part that holds the

data—but speeding up the input/output and adding special buffers (sort of

like a cache) makes DDR2 run much faster than regular DDR. DDR2 uses a

240-pin DIMM that’s not compatible with DDR (see Figure 4-15). Likewise,

the DDR2 200-pin SO-DIMM is incompatible with the DDR SO-DIMM.

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