"A Japanese magazine has managed to swap his MacInteltosh 1.83 GHz chip for a nice new Core Duo 2GHz CPU and get it to work. The article, published in Japanese in Boot magazine said that the Duo 2 worked flawlessly and the system information displayed the right 2GHz frequency.

Hardmac magazine has suggested that there is a number of reasons why this might work. You can overclock G3s and G4s by modifying the multiplying co-efficient. Intel and AMD lock those coefficient setttings inside the CPUs to stop this sort of thing, which is why overclockers have to always adjust their systems."