CompTIA A+ Certification All-in-One Exam Guide

NOTE The freeware CPU-Z program tells you the total number of slots on
your motherboard, the number of slots used, and the exact type of RAM in
each slot—very handy. CPU-Z not only determines the latency of your RAM
but also lists the latency at a variety of motherboard speeds. The media
accompanying this book has a copy of CPU-Z, so check it out or download it
from www.cpuid.com.
Mix and Match at Your Peril
All motherboards can handle different capacities of RAM. If you have three
slots, you may put a 2-GB stick in one and a 4-GB stick in the other with a
high chance of success. To ensure maximum stability in a system, however,
shoot for as close as you can get to uniformity of RAM. Choose RAM sticks
that match in technology, capacity, speed, and latency (CL).
Mixing Speeds
With so many different DRAM speeds available, you may often find yourself
tempted to mix speeds of DRAM in the same system. Although you may get
away with mixing speeds on a system, the safest, easiest rule to follow is to
use the speed of DRAM specified in the motherboard book, and make sure
that every piece of DRAM runs at that speed. In a worst-case scenario,
mixing DRAM speeds can cause the system to lock up every few seconds or
every few minutes. You might also get some data corruption. Mixing speeds
sometimes works fine, but don’t do your tax return on a machine with mixed
DRAM speeds until the system has proven to be stable for a few days. The
important thing to note here is that you won’t break anything, other than
possibly data, by experimenting.
Okay, I have mentioned enough disclaimers. Modern motherboards
provide some flexibility regarding RAM speeds and mixing. First, you can
use RAM that is faster than the motherboard specifies. For example, if the
system needs PC-19200 DDR4, you may put in PC-25600 DDR4 and it
should work fine. Faster DRAM is not going to make the system run any