Many components in a computer system unit produce large amout of heat during operation, including, but not limited to: the CPU, chipset, graphics card, and hard drives. This heat must be dissipated in order to keep these components within their safe operating temperatures. Overheated parts have a shorter life and may give sporadic problems resulting in system freezes or crashes. This is done mainly using heatsinks (to increase surface area) and fans (to move air).

System Cooling

This refers to cooling the entire system unit (as opposed to cooling individual parts - spot cooling), by ensuring good airflow throughout using fans. Typically, at the front of a 'tower' type system unit, there is a fan in the lower part drawing cool air from vents into the system. There may be a matching fan at the upper rear of the unit that forces the hot air out. This creates an 's' shaped path that must be clear of obstacles for it to work best.

If there is more air being forced into the system than being pumped out (due to an imbalance in the number of fans), this is referred to as a 'positive' airflow, as the pressure inside the unit would be higher than outside. A balanced or neutral airflow is the most efficient, although a slightly positive airflow results in less dust build up.

Spot Cooling

Passive Heatsink Cooling

This involves attaching a block of machined metal to the part that needs cooling. An adhesive may be used, or more commonly for a CPU, a clamp is used to affix the heatsink tight over the chip, with a thermally conductive pad or gel spread in-between. This block usually has fins and ridges to increase its surface area. The heat conductivity of metal is much better than that of air, and its ability to radiate heat is better than that of the component part it is protecting (usually an integrated circuit/CPU). Commonly found on older CPUs and parts that do not get very hot (such as the chipset).

Forced Air (Fan)

This is similar to passive heatsink cooling, except that a fan is attached to the heatsink, usually forcing air down onto it, to increase the amount of air coming in contact with the heatsink. This can increase cooling efficiency dramatically. Normally found modern CPUs and the processor on many modern graphics cards.

Peltier Cooling

This involves placing a special heatsink containing a Peltier effect heat pump in the surface which comes in direct contact with the component. The Peltier pump forces heat transfer at a higher rate that can ordinarily be achieved by conventional means, increasing the efficiency of the heatsink.

Liquid (Water) Cooling

Main article: Liquid cooling for computers

Heat Pipe

A heat pipe is a hollow tube containing a heat transfer liquid. As the liquid evaporates, it carries heat to the cool end, where it condenses and flows back to the hot end (under capillary force). Heat pipes thus have a much higher effective thermal conductivity than solid materials. In computers, the heatsink on the CPU is attached to a larger radiator heatsink. Both heatsinks are hollow as is the attachment between them, creating one large heat pipe that transfers heat from the CPU to the radiator, which is then cooled using some conventional method. This method is expensive and usually used when space is tight (as in small form-factor PC's), or absolute quiet is needed (computers used in audio production studios during live recording).

Causes of Heat Build Up

• Dust - Dust acts as a thermal insulator, and reduces the performance of heatsinks and fans.
• Poor Airflow (Turbulence) - Components and cabling cause friction (drag) and turbulent flow that reduce the amount of air flowing through a case, even possibly causing stable whirlpools of hot air in certain areas.

Cooling and Overclocking

Extra cooling is usually required by people who run parts of their computer (such as the CPU and graphics card) faster than manufacturer specifications, called overclocking. Increasing performance by this modification of settings results in a greater amount of heat generated. The installation of better, non-stock cooling may also be considered modding. Many overclockers simply buy more efficient, more expensive fan/heatsink combinations. A greater investment is involved in liquid cooling, but this is seen by many to be the ultimate in consumer level cooling.

There are also some related practices that have a positive impact in reducing system temperatures:

Heatsink Lapping

This is the smoothing and polishing of the contact (bottom) part of a heatsink to increase its heat transfer efficiency. Even a mediocre heatsink can be improved greatly by doing this. This is because, although smooth to the naked eye, most heatsinks made by machine tools have quite a rough surface characterized by ridges, which create regions of trapped insulating air. Polishing these down using a combination of fine sandpaper and abrasive polishing liquids can produce a mirror-like shine that is the main indicator of a very flat metal surface.

Use of Exotic Thermal Conductive Compounds

Some overclockers use specialty thermal compounds whose manufacturers claim to have a much higher efficiency than stock thermal pads. Heatsinks clean of any grease or other thermal transfer compounds have a very thin layer of these products applied, and then are placed normally over the CPU. Many of these compounds have a high proportion of silver as their main ingredient. The resulting difference in the temperature of the CPU is measurable, and percentage-wise, the heat transfer does appear to be much superior to stock compounds, but this often works out to a difference of less than a degree.

Use of Rounded Cables

Most PC's use flat ribbon cables to connect storage drives (IDE or SCSI). These large flat cables greatly impede airflow by causing drag and turbulence. Overclockers and modders often replace these with rounded cables, with the conductive wires bunched together tightly, to reduce surface area. Theoretically, the parallel strands of conductors in a ribbon cable serve to reduce cross-talk (signal carrying conductors inducing signals in nearby conductors), but there is no anecdotal evidence of rounding cables reducing performance. The rounded cables are also more aesthetically pleasing, and are available in a variety of colours.