Case fan Fans are used to move air through the computer case. The components inside the case cannot dissipate heat efficiently if the surrounding air is too hot. Case fans may be placed as
intake fans, drawing cooler outside air in through the front or bottom of the chassis (where it may also be drawn over the internal hard drive racks), or
exhaust fans, expelling warm air through the top or rear. Some
ATX tower cases have one or more additional vents and mounting points in the left side panel where one or more fans may be installed to blow cool air directly onto the motherboard components and expansion cards, which are among the largest heat sources. Standard axial case fans are 40, 60, 80, 92, 120, 140, 200 and 220 mm in width and length. As case fans are often the most readily visible form of cooling on a PC, decorative fans are widely available and may be lit with
LEDs, made of
UV-reactive plastic, or covered with decorative grilles. Decorative fans and accessories are popular with
case modders.
Air filters are often used over intake fans, to prevent
dust from entering the case and clogging up the internal components. Heatsinks are especially vulnerable to being clogged up, as the insulating effect of the dust will rapidly degrade the heatsink's ability to dissipate heat.
PSU fan While the
power supply (PSU) contains a fan with few exceptions, it is not to be used for case ventilation. The hotter the PSU's intake air is, the hotter the PSU gets. As the PSU temperature rises, the conductivity of its internal components decrease. Decreased conductivity means that the PSU will convert more of the input electric energy into thermal energy (heat). This cycle of increasing temperature and decreased efficiency continues until the PSU either overheats, or its cooling fan is spinning fast enough to keep the PSU adequately supplied with comparatively cool air. The PSU is mainly bottom-mounted in modern PCs, having its own dedicated intake and exhaust vents, preferably with a dust filter in its intake vent.
CPU fan Le Grand Macho RT functioning Used to cool the
CPU (central processing unit) heatsink. Effective cooling of a concentrated heat source such as a
large-scale integrated circuit requires a heatsink, which may be cooled by a fan; use of a fan alone will not prevent overheating of the small chip.
Graphics-card fan , a
PCI Express 3.0 ×16
graphics card, using two fans for cooling Used to cool the
heatsink of the
graphics processing unit or the memory on
graphics cards. These fans were not necessary on older cards because of their low power dissipation, but most modern graphics cards designed for 3D graphics and gaming need their own dedicated cooling fans. Some of the higher powered cards can produce more heat than the
CPU (dissipating up to 350 watts), so effective cooling is especially important. Since 2010, graphics cards have been released with either
axial fans, or a centrifugal fan also known as a blower, turbo or squirrel cage fan.
Chipset fan Used to cool the heatsink of the northbridge of a motherboard's
chipset; this may be needed where the
system bus is significantly
overclocked and dissipates more power than as usual, but may otherwise be unnecessary. As more features of the chipset are integrated into the
central processing unit, the role of the chipset has been reduced and the heat generation reduced also.
Hard-drive cooling Fans may be mounted next to or onto a
hard disk drive for cooling purposes. Hard drives can produce considerable heat over time, and are heat-sensitive components that should not operate at excessive temperatures. In many situations, natural convective cooling suffices, but in some cases fans may be required. These may include: • Faster-spinning hard disks with greater heat production. ( less expensive drives rotated at speeds up to 7,200 RPM; 10,000 and 15,000 RPM drives were available but generated more heat.) • Large or dense arrays of disks (including server systems where disks are typically mounted densely) • Any disks which, due to the enclosure or other location they are mounted in, cannot easily cool without fanned air
Multiple purposes A case fan may be mounted on a radiator attached to the case, simultaneously operating to cool a liquid cooling device's working fluid and to ventilate the case. In
laptops, a single blower fan often cools a heat sink connected to both
CPU and
GPU using
heat pipes. In
gaming laptops and
mobile workstations, two or more heavy duty fans may be used. In
rack-mounted servers, a single row of fans may operate to create an airflow through the chassis from front to rear, which is directed by passive ducts or shrouds across individual components'
heat sinks.
Other purposes Fans are, less commonly, used for other purposes such as: • Water-cooling radiator transfers a lot of heat, and radiator fans have large static pressure (opposed to case fans that have high airflow) for dissipating heat. • Laptop computers lack large openings in the case for warm air to escape. The laptop may be placed on a cooler – somewhat like a tray with fans built in – to ensure adequate cooling. • Some high-end machines (including many servers) or when additional reliability is required, other chips like
SATA/
SAS controller, high speed networking controllers (40Gbps Ethernet,
Infiniband), PCIe switches, coprocessor cards (for example some Xeon Phi), some
FPGA chips, south bridges are also actively cooled with a heatsink and a dedicated fan. These can be on a main motherboard itself or as a separate add-on board, often via PCIe card. •
Expansion slot fana fan mounted in one of the
PCI or
PCI Express slots, usually to supply additional cooling to the graphics cards, or to expansion cards in general. •
Optical drive fansome internal CD and DVD burners included cooling fans. •
Memory fan modern
computer memory can generate enough heat that active cooling may be necessary, usually in the form of small fans positioned above the memory chips. This applies especially when the memory is overclocked or
overvolted, or when the memory modules include active logic, such as when a system uses
Fully Buffered DIMMs (FB-DIMMs). However, with newer lower voltages in use, such as 1.2v
DDR4, this is less commonly needed than used to be the case. Most of the time memory modules, located close to CPU will receive enough of the air flow from the case or CPU fan, even if the air from CPU fan and radiator is warm. If the main CPU is water cooled, this small amount of airflow might be missing, and additional care about some airflow in a case or a dedicated memory cooling is required. Unfortunately most memory modules do not provide temperature monitoring to easily measure it. == Physical characteristics ==