Creating a computer cooling system

Random crashes can make using a PC frustrating, and the first thing many people check is the drivers. But there can be other culprits.

Reliability problems can be caused by poor cooling. A common symptom is when your PC exhibits problems only after it has been turned on for a while, or if things become worse in hot weather such as this summer’s UK heatwave.

In extreme cases a poorly cooled PC may simply shut down without warning. And, perhaps, never turn on again.

For many people, taking the DIY route and building their own PC is the best way to get the system they want, but one of the most difficult things to get right is cooling. In recent years CPUs, bridge chips, graphics cards and hard disks have increased their heat output, and while this trend may be reversing with Intel’s new dual-core designs – at least for CPUs – the inside of a modern PC is getting warmer.

With so many heat sources spread throughout the case, a simple ‘slap a fan on it’ approach needs to be replaced by integrated cooling design. There’s surprisingly little useful information available on how to go about this, and one of the most irritating things about cooling devices is that the manufacturers rarely publish sufficient details to allow you to compare products.

For a high-performance PC, cooling design can’t just be left to chance. A properly designed system balances temperatures against noise and keeps the cost of the cooling components under control. The result should be a reliable, quiet system that helps to extend the life of the individual components. In this feature we’ll see what can realistically be done to achieve that.

Have a plan
Although the internal layouts of most PCs are broadly similar, it’s the details that make the difference in cooling design. One of the first choices in building a PC is the motherboard and it’s the position of the heat-generating components on this that should be the starting point for your thermal design.

The CPU puts out the most heat, followed by the graphics card. Dual-CPU boards are more difficult to cool than single-CPU boards because two processors generate twice as much heat, and one CPU will be closer to the power supply air inlet than the other.

Hard disks should not be overlooked either, as current high-capacity designs can become frighteningly hot. Look for a case that allows you to fit a local fan, with an intake for outside air, to cool the hard disks if required.

A case in point
The next step is to choose a case, bearing in mind the location of the CPU, bridge chip, graphics card and memory. Cable routing should also be considered. Some case and motherboard combinations force you to put peripherals such as hard disks and DVD drives in awkward positions relative to the motherboard connectors, resulting in poor cable routing.

It’s important to buy a case that suits your components. Buying a really small case that has no room for fans when you’re putting together a cutting-edge dual-CPU system isn’t going to help keep everything cool.

The volume of air inside the case acts as a heat store: given the same heat input, the air in a small case will rise to a higher temperature than the air inside a larger case. Also, big cases often allow for a better layout and easy cable routing. Wide cases allow for space above the I/O cards so that air can escape and circulate around them.

An all-metal case, particularly an aluminium one, will run cooler than a mostly plastic one. Cases with sound-damping treatment tend to run at a higher temperature, because the sound-damping treatment also acts as heat insulation.

There’s a typical engineering trade-off here; a good-size aluminium case with sufficient airflow and an appropriate choice of CPU and graphics cooling device may actually be quieter than a design with sound insulation that needs better cooling fans.

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