Hardware Reference
In-Depth Information
• For high-current processors, there are several alternatives. The CPU
coolers that AMD and (particularly) Intel bundle with their retail-
boxed performance processors are much better than they were a few
years ago. Even with a hot processor, a retail-boxed CPU cooler does a
reasonably good job of cooling the processor with little noise.
• To minimize noise with any processor, install a Thermalright ( http://
www.thermalright.com ) or Zalman ( http://www.zalmanusa.com ) unit.
For processors with low to midrange power consumption, some of
these premium coolers can be run in silent (fanless) mode, which
completely eliminates CPU cooler noise.
monITorIng cPU TEmPEraTUrE
Modern motherboards provide temperature sensors at
important points such as the CPU socket. The motherboard
reports the temperatures reported by these sensors to the
BIOS. You can view these temperatures by running BIOS
Setup and choosing the option for temperature reporting,
which can usually be found under Advanced Hardware
Monitoring, or a similar menu option. Alternatively, most
motherboards include a monitoring utility—Intel's, for
example, is called the Intel Active Monitor —that allows you
to monitor temperatures from Windows rather than having
to run BIOS Setup.
that your CPU cooler and system fans are doing their jobs
properly.
An idle temperature of 30° C or lower is ideal, but that is not
achievable with the hottest processors, which idle at 40° C or
higher with any but the most efficient CPU coolers. In general,
a CPU cooler that produces an idle temperature of 40° C or
lower suffices to cool the CPU properly under load.
If you want to verify temperature under load, run an applica-
tion that loads the CPU with intense calculations, ideally
with lots of floating-point operations. Two such applications
we have used are the SETI@home client ( http://setiathome.
ssl.berkeley.edu ) and the Mersenne Prime client ( http://
mersenne.org ). Run the application for an hour to ensure
the CPU has reached a steady-state temperature and then
use the temperature monitoring application to view the
temperature while the application is still running.
CPU temperature can vary dramatically with changes in
load. For example, a CPU that idles at 30° C may reach 50° C
or higher when it is running at 100% capacity. A hot-running
CPU may reach temperatures of 70° C or higher under load,
which is perilously close to the maximum acceptable tem-
perature for that processor, so it is very important to verify
CPU Coolers and Motherboard Compatibility
If you choose an aftermarket CPU cooler, verify that it is physically compatible with
your motherboard and case. Quiet CPU coolers often use very large heatsinks, which
may conflict with protruding capacitors and other motherboard components. Most
premium CPU cooler manufacturers post motherboard compatibility lists on their
websites. It's just as important to verify that the CPU cooler fits your case. Some
high-end CPU coolers are physically huge. Before you buy one of those, make sure
the chassis structure won't prevent it from being installed, and make sure there's
sufficient clearance between the motherboard and case cover that you'll be able to
reinstall the cover with the CPU cooler in place.
 
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