Hardware Reference
In-Depth Information
Cooling Fans and Heat Sinks
With millions of transistors working in close proximity, processors generate heat. This is
a result of one of the simpler laws of physics involving electrical energy. Heat is caused as
the transistor restricts the fl ow of electrical current. The energy has to go somewhere, so
it's released as heat. Heat generation is highest when a processor is busy, such as when it's
drawing a complex graphic or juggling many applications at once.
Without external cooling, a processor would overheat and shut down almost
immediately after the system started up. Therefore, all modern computers have some type
of heat-displacement system. A cooling system can be either passive or active. A
passive
cooling system
contains no moving parts; an
active cooling system
does something active
to circulate either water or air to displace the heat.
The most common type of passive cooling system is a heat sink. A
heat sink
is a block
of heat-conductive metal that touches the processor and draws the heat away from it. Some
small, less powerful processors, such as the one in a cell phone or hand-held gaming device,
can stay cool enough to function with only a passive heat sink. Figure 1.4 shows a passive
heat sink that might be used to cool one of the nonprocessor chips on a motherboard, such
as the main chip in the chipset that controls motherboard operations.
FIGURE 1.4
A passive heat sink
In today's PCs, passive cooling usually isn't enough for the processor to stay cool; a heat
sink is combined with a fan that blows across it, further helping to dissipate the heat as it's
drawn off. Figure 1.5 shows an example of an active heat sink.
