Overclockers waged a battle of ice against fire at Computex last week in Taipei, pushing the performance limits of Intel's CPUs to 5GHz. The hobbyists, who are becoming an increasingly common sight at IT trade shows, are perfecting the art of pushing processors to their limits.

"Overclocking is taking a basic system and modifying the settings to get more performance out of your system," said Fugger, a US overclocker who like others prefers to go by a nickname.

"We take a processor you can buy in the store, like we have here, and we're pushing these up to 4.6 or 4.7GHz," he said, indicating a couple of computer motherboards hooked up to cooling equipment designed to keep the processor below minus 100 degrees Celsius. The demonstration on the stand of Taiwanese motherboard maker Abit used Intel Core 2 Quad processors that usually run at 2.66GHz.

The speed of a processor is typically determined by two things: the speed of the interface that connects the chip to the rest of the computer (called the front-side bus) and a multiplier. For example, a 500MHz front-side bus and a multiplier of three means the chip runs at 1.5GHz. By changing these values the chip can be made to run faster.

The result is not just more speed but lots of heat. Typically a processor is cooled with a large metal heat sink and fans, but that's not enough for overclocked chips so a more imaginative method is needed.

"I have a pressurised 22 psi (pounds per square inch) liquid nitrogen cooler, we're feeding it through copper tubing through a stainless steel valve into a king-pin pot. This is a copper pot that sits on top of the processor and we actually feed the liquid nitrogen directly into the processor," said Fugger as a fellow overclocker from Sweden opened a valve and white clouds of vapour began to billow out of the system.

The system, Fugger maintains, is quite safe and is one that he uses at home alongside more elaborate systems that rely on coupling two or three refrigeration compressors together to get the desired temperature.

"We can bring the CPU down to minus 200 degrees Celsius but we usually keep it at minus 120," said Crotale, the Swedish overclocker, as he played with the system. "At a certain point the CPU becomes like a super conductor so it just shorts out the CPU. We need to keep it as close to that point as possible to get the maximum performance."