Feature: Build a living-room PC

Passive or active cooling?
Cooling systems with no fans at all can only be recommended in certain situations, as the graphics card, processor and motherboard can all get very hot.

Tests in our labs show that in a system with passive cooling only and no fan, temperatures of nearly 180ºC can arise on the motherboard. For this reason, the motherboard should always be supplied with cool air.

A good CPU fan is usually enough if the motherboard itself is fitted with passive cooling elements. For living-room PCs motherboards with integrated fans are not really suitable, because their high speed (about 2,500rpm) makes the mini-fans too noisy.

Hot 3D
Until now, standard 3D graphics cards such as those in the Nvidia or ATI reference designs have been unsuitable for use in a quiet environment as they are usually only made with noisy, undersized, cheap fans.

To get the best possible 3D performance in our quiet living-room PC, we used the passively cooled Asus EN7800GT, which is at present the fastest passively cooled graphics card on the market.

The card uses Nvidia’s 7800GT chip which is factory-tuned and uses a 420MHz core with a memory speed of 620MHz (400/500MHz are normal).

This means that the Asus is already overclocked when sold – with a full three-year warranty. Normally, if you overclock a card it immediately invalidates the warranty.

A movable cooling radiator element is linked to the socket with a heatpipe. The hinged cooling construction is designed to be adjusted so that it sits above the CPU fan, which then sucks the air from the graphics card heatpipe: this can have a temperature of up to 70ºC.

The CPU fan has to work hard so that the aluminium cooling element can dissipate enough heat, or when the temperature reaches 105ºC the graphics card will throttle back and become noticeably slower.

Casing fans ensure cooling
A switch-controlled extra fan in the right place will allow the card to be cooled even more if need be. This lets it run at full power – its performance level is 10 per cent above that of a conventional 7800GT which means that passive cooling and top performance can go together.

If the machine is not being used for gaming, the fan can simply be turned off. The large CPU fan provides enough cool air when the computer’s in normal use.

However, the EN7800GT Top Silent used in our living-room PC is taller than a standard amplifier case (15cm). This means that you won’t be able to avoid having to make a suitably sized opening in the top of the casing, so that everything fits inside.

If you don’t want to do this, use a standard graphics card instead and swap the active graphics card cooler for one of the special models from Arctic Cooling.

The Silencer VGA cooler range is available for most popular ATI and Nvidia models and installation is straightforward. This quiet cooling system costs around £19 and has a maximum noise level of 36dBA.

If you don’t want to do any modification work, take a look at the Asus or HIS graphics cards. Some of these cards come with the powerful, but quiet, Arctic Cooling fan.

But a word of caution: graphics cards with this fan require a lot of space and usually block the PCI slot next to the PCI Express slot.

If you don’t need top 3D speed, then you can do without an external graphics card altogether: the onboard Nvidia graphics chip, which is passively cooled, is adequate for video playback and DVD encoding.

The whole point of our living-room PC is that just about anyone can build one without much outlay over and above a normal PC.

For the actual work, you only need some simple tools – a soldering iron, a screwdriver and a miniature electric rotary tool (Dremel or similar).

The amount of work involved is reasonable; it shouldn’t take you more than a weekend, as long as you have all the parts to hand.

And the added beauty of this project is that you can make whatever modifications to our basic plan that you fancy – the only limit is your ingenuity.