If your Beige G3 uses a "Royal Tech" VRM (voltage regulator module) module located on your logic board, then you cannot run any speed G4 upgrade - from any manufacturer - unless you replace it. Apple used this VRM on only a small percentage of Beige G3 Models. The word Royal is printed on the module for easy identification and if you have put a G4 into a machine with the Royal VRM, the likely result is the burn out of the G4 as well as the logic board.