Xtrem will release a £2,000 1.2GHz PowerPC in January, the company says.

The Xtrem Mac will feature a proprietary cooling system, designed to reduce the running temperature of the processor enough so that it can be "overclocked" to run at 1.2GHz. If tried at room temperature, the processor would fry.

The XtremMac is a customized Power Mac G4 in an aluminium case. The project was announced last summer, but has met with a sceptical response from industry insiders, who are doubtful of Xtrem's claims.