Hardware Reference
In-Depth Information
Just because a processor fits in the socket (or slot) on your motherboard does not mean it
will work. For a processor to work in a system, the following things are required:
• The CPU must fit in the socket. Refer to Chapter 3 , “ Processor Types and Specifica-
tions ,” for a complete guide to the various CPU socket types and which processors are
compatible with them.
• The motherboard must support the voltage required by the CPU. Modern mother-
boardssetvoltagesbyreadingvoltageID(VID)pinsontheprocessorandthensetting
theonboardvoltage regulator module (VRM)totheappropriate settings. Olderboards
might not support the generally lower voltage requirements of newer processors.
• The motherboard ROM BIOS must support the CPU. Modern boards also read the
CPU to determine the proper FSB (or CPU bus) speed settings as well as the clock
multipliersettingsfortheCPU.ManyCPUshavedifferentrequirementsforcacheset-
tings and initialization, as well as for bug fixes and workarounds.
• The motherboard chipset must support the CPU. In some cases, specific chipset mod-
els or revisions might be required to support certain processors.
Before purchasing anupgradedprocessorforyoursystem, youshouldfirstcheckwiththe
motherboard manufacturer to see whether your board supports the processor. If so, it will
meet all the requirements listed previously. Often, BIOS updates are available that enable
newerprocessorstobesupportedinolderboards,beyondwhatwasoriginallylistedinthe
manualwhenyoupurchasedtheboard.Theonlywaytoknowforsureistocheckwiththe
motherboard manufacturer for updated information regarding supported processors for a
particular board.
Inoneexample,Ihadpurchasedanewmotherboardandprocessorforanewsystembuild,
and upon initial power-on, the system didn't work at all. Upon investigation, I found that
thenewmotherboardIhadpurchaseddidindeedsupporttheprocessorIhadinstalled, but
only if the BIOS was upgraded to the latest version. Unfortunately the board I had must
have been sitting on the shelf awhile because it came with an older BIOS version. All I
had to do to solve the problem was to upgrade the BIOS, but how was I to do that since
the board wouldn't even run with the processor until after the BIOS had been upgraded. I
was in a classic chicken-before-the-egg situation. In the end I found a friend who had an
olderprocessor,onethatwouldworkwiththeolderBIOSinmymotherboard. Iborrowed
the chip and installed it just long enough to perform the BIOS upgrade; then I removed
theborrowedchipandreinstalledthenewoneIhadoriginallypurchased.Thesystemthen
worked perfectly.
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