Processor Types and Specifications - Upgrading and Repairing PCs - page 164

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One of the best reasons to use the motherboard-based power connectors for the fan is that
most system BIOS setup programs can display the fan performance and report it to a system
monitoringprogram.Becausesomeprocessors—particularlyolderAthlonprocessors—canbe
destroyed in a few moments by a malfunctioning processor heatsink fan, this feature can help
prevent a disaster inside your system.
If you need to purchase an active heatsink, be aware that some on the market are of poor
quality.Thebadoneshavefanmotorsthatusesleevebearings,whichfreezeupafterashort
life. I recommend only fans with ball-bearing motors, which last about 10 times longer
thanthesleeve-bearingtypes.Ofcourse,theycostmore—butonlyabouttwiceasmuch,so
you'll save money in the long run.
Newerfansincludefour-wirepowerconnectors,whichfeaturethestandardpower,ground,
and tach wires found in three-wire fans, but they also add a fourth wire for fan-speed con-
trol. These are known as PWM (Pulse Width Modulation) fans because they use pulse
width modulation signals from the motherboard to control their speed more precisely and
with more variations in speed. Standard three-wire fans have internal thermal resistors
(thermistors) that control fan speed, and these normally offer only two-speed operation.
WiththePWMsetup,themotherboardcanmonitorsystemandprocessortemperatures and
variably control the fan speed to maintain the desired temperatures.
Heatsinks designed for LGA775, LGA1156, or LGA1366 sockets usually include plastic
retainer clips that snap into holes in the motherboard. To install this type of heatsink, you
merely align the topsofthe clips suchthat the arrowsare rotated all the waytothe left (op-
posite the direction of the arrow) and then press the tops down until the bottom parts click
and lock into the holes in the motherboard. To remove the heatsink, you insert a flat blade
screwdriver into the slot under the arrows and then rotate the tops in the direction of the
arrows. As you rotate each clip, it will pop out of the motherboard. Figure 3.49 shows an
active heatsink for Socket LGA1155 processors, featuring these snap-in retainers.
Figure 3.49 LGA1155 boxed processor heatsink showing snap-in retainers and a four-wire PWM fan.