Overclocking Powermac G4 400 AGP
Hi Ive been reading around and some people say theyve got an overclocked G4 400 up to 450 but some have said its not possible, is it and if so hows it done?
PowerMac G4 400 AGP, Mac OS X (10.4.8)
Hi
It's possible to overclock the processor by changing the bus multiplier setting from 4 to 4.5. This will result in the processor running at 4.5 times the bus speed (4.5 x 100MHz = 450MHz) rather than 4 times (4 x 100MHz = 400MHz). The bus multiplier settings are set via a series of small resistors on the CPU daughter card. By adding and/or removing resistors, you can increase or decrease the multiplier, hence overclocking or underclocking the processor.
The following link contains info on the dual 500MHz processor card, although the concept is the same:
http://www.xlr8yourmac.com/G4ZONE/sawtooth/DualG4_550mods.html
As for whether the processor is stable at higher frequencies, it depends. It will have been guaranteed to run at 400MHz by Motorola under certain environmental conditions. It may or may not work at 450MHz, every processor will be different. In most cases I expect it would work, but you may well experience sporadic freezes, crashes or kernel panics etc. When Motorola first introduced the G4, they had yield problems with the higher frequency chips, so it seems doubtful they'd be overclockable to any degree.
It's possible to overclock the processor by changing the bus multiplier setting from 4 to 4.5. This will result in the processor running at 4.5 times the bus speed (4.5 x 100MHz = 450MHz) rather than 4 times (4 x 100MHz = 400MHz). The bus multiplier settings are set via a series of small resistors on the CPU daughter card. By adding and/or removing resistors, you can increase or decrease the multiplier, hence overclocking or underclocking the processor.
The following link contains info on the dual 500MHz processor card, although the concept is the same:
http://www.xlr8yourmac.com/G4ZONE/sawtooth/DualG4_550mods.html
As for whether the processor is stable at higher frequencies, it depends. It will have been guaranteed to run at 400MHz by Motorola under certain environmental conditions. It may or may not work at 450MHz, every processor will be different. In most cases I expect it would work, but you may well experience sporadic freezes, crashes or kernel panics etc. When Motorola first introduced the G4, they had yield problems with the higher frequency chips, so it seems doubtful they'd be overclockable to any degree.