Been a while but I thought the iMac processor card had cache chips on it. If so, wouldn't that be limiting the speed?
Depends on whether he's clocking it up by increasing the bus speed, or by increasing the multiplier. The "proper" method in this case would be to keep the iMac's original bus speed and increase the G4's clock speed by increasing the clock multiplier. With the original bus speed, the cache chips would see no difference. I would not be surprised at all if the iMac has little or no head room for bus speed changes.
Very cool work, BTW. Breathtaking. Which is kind of weird to say about soldering, but what the h---, it just is.
Hmmm, could one take an old G3 ZIF and replace the vanilla 750 with a 750FX or GX and remove the cache chips? Probably not, because the L2 is internal on the FX and GX, so the pinouts are probably different. It sure would be nice to increase the supply of 1 GHz G3 upgrades with L2 cache running at full CPU speed... We could design new ZIF boards easily enough, but that darn pin grid array header was impossible to find the last time I looked for it. OTH, we didn't have Ali Express back then.
Hmmm. It might be worth comparing the pinout of the 750FX/GX to the pinout of the 603/740 though. If a 740 would be an improvement, then a 750GX with 1 MB of internal L2 cache running at 1 GHz would be just the ticket. 20X bus multiplier for the win....
Voltage regulation is typically by an adjustable regulator whose level is set by two resistors. Not always, but that's normal. It shouldn't be too difficult to find the Vreg but it might not be on the CPU card. It is not, in the Beige G3.