LeopardAssist temporarily patches your NVRAM to trick Leopard into thinking you have an 867mhz CPU.
Testing is being constantly conducted on various systems, so far we have positive reports from users of Sawtooth, Digital Audio, Gigabit Ethernet and Cube Macs. Other systems including the QuickSilver and Mirrored Drive Doors G4s, iMacs and eMacs are in active testing from the community. A list of compatible systems is available
here.
Requirements: OS X 10.3.9 or later.