I didnt realise the G3 was pin comptatible with the G3.
That's interesting. If it worked it wuld be impressive, but I wouldn't expect a huge speed increase - even the 603 is held back by the memory bus on the blizzardPPC. You could probably clock it to 300MHz using 60MHz / x5 multiplier.
Hardware aside, under warpos, you'd probably need to roll your own warpHW.library for it too - pin/voltage compatible or not, the supervisor model of the chip probably isn't going to be the same.
