Well, you can over clock thru the OF Firmware.
reboot, and hold down the "CMD","OPT","O" +"F" keys.
enter the NVRAMRC editor (<enter> shows you should press the"return" key)
nvedit<enter>
Then type the following script exactly - including the spaces.
" /" select-dev<enter>
7efdc44 " clock-frequency" get-my-property 2drop !<enter>
" /cpus/PowerPC,G4@0" select-dev<return>
1fca0554 " clock-frequency" get-my-property 2drop !<enter>
7efdc44 " bus-frequency" get-my-property 2drop !<enter>
1fbf711 " timebase-frequency" get-my-property 2drop !
Type ^C (Control + 'C') to exit nvedit
save the script:
nvstore<enter>
enable the NVRAMRC by typing :
setenv use-nvramrc? true<enter>
and then reboot to the new time constant by typing
reset-all<enter>
This will save stuff you changed and reboot at a new speed.
Works for my G4 single. Changes from 500 for the CPU speed to 533, and buss speed goes from 100 to 133. About 1% or so.