Hardware Reference
In-Depth Information
• Refrigeration
Each of these uses a liquid or vapor to absorb the heat of the processor or other compon-
ents and take that heat to a heat exchanger where it must eventually be dispersed to the
air.So,allliquidcoolinginvolvesaircoolingaswell;itjustremovestheexchangeofheat
to the air to a remote place. Also, the heat exchanger (radiator) used can be much larger
thanwhatwouldfitdirectlyontheprocessororotherchips,whichisanotherreasonliquid
cooling offers much greater cooling capacity.
Of all the types of liquid cooling available, heat pipes are the only type that is practical
and cost-effective in production-level PCs. Water cooling and especially refrigeration are
limited to those who are pursuing extreme overclocking and are willing to pay the high
prices and put up with all the drawbacks and disadvantages that come with these two op-
tions.
Thermally Advantaged Chassis
PC power supplies have always contained a fan. For many years, that single fan in the
power supply bore the responsibility of cooling not only the supply, but also the entire
system and even the processor. In fact, PCs prior to the 486 didn't even use heatsinks on
the processor because they generated only a couple of watts of heat. Passive heatsinks
first became a standard fixture on processors with the 486DX2 in 1992, which used up to
5.7Wofpower.ActiveheatsinksfirstappearedontheretailPentiumprocessorsfromIntel
(called Overdrive processors) and became a standard fixture on boxed or retail Pentium II
and III and AMD Athlon models in 1997 and later. Most chassis up until that time did not
incorporate a cooling fan, except for what was in the power supply.
Chassis fans first became popular in OEM systems in the mid-1990s because they usually
used less expensive passive heatsinks on the processor. It was more efficient to use a
single chassis fan to cool both the chassis and the processor and save money by using a
passiveheatsink(withoutafan)ontheprocessor.By2000,withthePentium4,manysys-
tems began using both an active processor heatsink (with a fan) and a chassis fan. Most
modern systems include three fans—one in the power supply, one in the active heatsink
onthe processor,andoneforthe rear ofthe chassis. Some systems have additional fans(a
secondrearfanandafront-mountedfanforcoolingharddiskdrivesarepopularadd-ons),
but three is the most common and most cost-effective design.
Unfortunately, with high-performance processors reaching and even exceeding the 100W
power level, it has become impossible for a standard chassis design to cool the system
withoutresortingtoaddingmorefansorusingmoreexotic(andexpensive)liquidcooling
setups. A minor breakthrough in chassis design has occurred that can allow even pro-
