Editing Computer cooling (section)

===Desktops===
[[File:Computer case coolingair flow.png|thumb|right|Illustration of the airflow of the cooling air in a computer case during computer cooling]]
[[Desktop computer]]s typically use one or more fans for cooling. While almost all desktop power supplies have at least one built-in fan, power supplies should never draw heated air from within the case, as this results in higher PSU operating temperatures which decrease the PSU's energy efficiency, reliability and overall ability to provide a steady supply of power to the computer's internal components. For this reason, all modern ATX cases (with some exceptions found in ultra-low-budget cases) feature a power supply mount in the bottom, with a dedicated PSU air intake (often with its own filter) beneath the mounting location, allowing the PSU to draw cool air from beneath the case.

Most manufacturers recommend bringing cool, fresh air in at the bottom front of the case, and exhausting warm air from the top rear{{Citation needed|date=December 2011}}. If fans are fitted to force air into the case more effectively than it is removed, the pressure inside becomes higher than outside, referred to as a "positive" airflow (the opposite case is called "negative" airflow). Worth noting is that positive internal pressure only prevents dust accumulating in the case if the air intakes are equipped with dust filters.<ref>{{cite web|url=http://www.technibble.com/case-cooling-the-physics-of-good-airflow/2/|title=Case Cooling – The Physics of Good Airflow – Technibble|date=8 September 2006|access-date=4 September 2012|archive-url=https://web.archive.org/web/20120904104040/http://www.technibble.com/case-cooling-the-physics-of-good-airflow/2/|archive-date=4 September 2012|url-status=live}}</ref> A case with negative internal pressure will suffer a higher rate of dust accumulation even if the intakes are filtered, as the negative pressure will draw dust in through any available opening in the case

The air flow inside the typical desktop case is usually not strong enough for a passive CPU heatsink. Most desktop heatsinks are active including one or even multiple directly attached fans or blowers.