CompTIA A+ Certification All-in-One Exam Guide

Figure 4-19 Stick of ECC DDR3 with 9 memory chips
You might be tempted to say, “Gee, maybe I want to try this ECC RAM.”
Well, don’t! To take advantage of ECC RAM, you need a motherboard
designed to support ECC. Only expensive motherboards for high-end systems
use ECC. The special-use-only nature of ECC makes it fairly rare in desktop
systems. Plenty of techs with years of experience have never even seen ECC
RAM.
NOTE Some memory manufacturers call the technology error checking
and correction (ECC). Don’t be thrown off if you see the phrase—it’s the
same thing, just a different marketing slant for error correction code.
Registered and Buffered Memory
When shopping for memory, especially for ECC memory, you are bound to
come across the terms registered RAM or buffered RAM. Either term refers to
a small register installed on some memory modules to act as a buffer between
the DIMM and the memory controller. This little extra bit of circuitry helps
compensate for electrical problems that crop up in systems with lots of
memory modules, such as servers.
The key thing to remember is that a motherboard will use either buffered
or unbuffered RAM (that’s typical consumer RAM), not both. If you insert the
wrong module in a system you are upgrading, the worst that will happen is a
blank screen and a lot of head scratching.