CompTIA A+ Certification All-in-One Exam Guide

Figure 4-1 Mass storage holds programs, but programs need to run in RAM.
You saw in Chapter 3, “CPUs,” that the CPU uses dynamic random access
memory (DRAM) as RAM for all PCs. Just like CPUs, DRAM has gone
through evolutionary changes over the years, resulting in improved DRAM
technologies such as SDRAM, RDRAM, and DDR RAM. This chapter starts
by explaining how DRAM works, and then discusses the types of DRAM
used over the past several years and how they improve on the original
DRAM. The third section, “Working with RAM,” goes into the details of
finding and installing RAM. The chapter finishes with troubleshooting RAM
problems.
Historical/Conceptual
Understanding DRAM
As discussed in Chapter 3, DRAM functions like an electronic spreadsheet,
with numbered rows containing cells and each cell holding a one or a zero.
Now let’s look at what’s physically happening. Each spreadsheet cell is a
special type of semiconductor that can hold a single bit—one or zero—by
using microscopic capacitors and transistors. DRAM makers put these
semiconductors into chips that can hold a certain number of bits. The bits
inside the chips are organized in a rectangular fashion, using rows and