What Causes Computer Systems to Heat Up

While most components in your computer system generate heat, some components cause more heat than others.
For example, your Central Processing Unit (CPU) which is most in use even during normal operations is one of the main components that needs proper cooling to stay functional. Your Graphics Card (Graphics Processing Unit, GPU,) also needs special cooling, usually already built into the card itself. This is especially true for gamers, where the GPU is under a heavier load than it would normally be.

Another component that can generate large amounts of heat is the computers’ Random Access Memory (RAM). While generally this is not as much of an issue, some newer and faster RAM modules will come with a pre-assembled heat sink to help offset the extra heat that is caused by the faster speeds.
With all of these components each causing heat, they also heat each other up. A CPU’s heat might further raise the graphics card’s heat and vice versa. Heat is then dissipated through cooling mediums, including the case itself, airflow, heat sinks, etc.

Above: Dusty Heat Sink

Heat can also be caused by poor airflow. If airflow is obstructed by excess dust, hot air cannot be vented out of the system, and builds up inside, as shown in the image above. Obstructed airflow can also be caused by improper orientation of fans and components being in the way.
Aside from poor airflow, improper application of thermal compounds can cause heat sinks to lose efficiency and cause more heat within the system.

So How Do You Keep Heat Under Control?

There are many ways to keep different components from overheating. I’ll go over each of the most common cooling methods used in today’s consumer computer systems — heat sinks, fans, and thermal compounds — as well as some less common cooling methods that are not yet fully mainstream, but still an important part of high-end computer systems (liquid cooling).

Heat Sinks

One of the most common cooling components is the heat sink. Heat sinks can be found on most computer components including the CPU, Graphics Cards, RAM, and other integrated circuits.
There are two types of heat sinks: passive heat sinks and active heat sinks.

Above: CPU and chipset heat sinks

Passive heat sinks are essentially just pieces of aluminum, or more recently, copper, affixed using thermal compounds onto a computer chip that normally produces heat. Heat is then transferred through the conductive thermal compound into the metal, and is redistributed away from the chip itself. While this method works well for older CPUs and chips, newer and faster ones will require a more powerful cooling solution, such as an active heat sink.
Active heat sinks are similar to passive ones, except they have a fan attached. The fan helps to pull heat away from the heat sink allowing it to cool more effectively. You will usually see active heat sinks in graphics cards, and even larger active heat sinks in CPUs. Active heat sinks do require more care, as with the addition of a fan, dust is more susceptible to enter the heat sink and will require cleanings and care more often.

Fans

Fans, more specifically, case fans, help to cool your computer case by (usually) pulling cold air in through the front of the PC case, and blowing it out of the back.
This is not always the case though, as each PC builder has their own cooling preferences, and others may actually add in case fans causing their heating methods to be counterproductive. An example of a counterproductive fan setup would be all fans pulling air in. This can cause an excess of dust, as well as no way for heat to escape.

Above: Case fan with blue LEDs

Aside from case fans, there are also other types of fans available.
PCI slot fans, or blowers, are one way to increase the flow of air out of the back of the PC case. Hard drive (HDD) fan modules are usually made up of two small fans attached to the exposed side of an internal hard drive; this helps to pull heat away from faster or more active hard drives. Most internal power supply unites (PSUs) will have an internal fan pulling air in and another blowing air outside of the computer case. Fans can also be found as part of active heat sinks in CPUs, graphics cards, and chipsets.
The most common fan size ranges between 40mm and 140mm; though fans as large as 240mm are starting to emerge in the mass market and in specialty cases.

Water Cooling

Water cooling is generally only used in high-end systems and gaming systems.
Water dissipates heat more efficiently than heat sinks and fans. Water cooling systems consist of a pump that pumps water across multiple components within the system. Most often, water cooling systems work to actively cool the CPU and graphics card, but modular systems allow the connection to other components within the PC. Water cooling can also be much quieter than using more conventional cooling methods like fans.

Above: Liquid cooling

While there are many upsides to using water cooling, there are also a few major downsides.
Not only are water cooling systems much more complex, but they are also a more dangerous build if not done properly. Even a small leak can turn disastrous. If a leak is present, the coolant can damage internal components including the motherboard itself.