Quicksilver CPUs will generally work in G4 towers going back to the Sawtooth, but in everything but a DA will run at 75% of their rated clock speed.
In addition, Quicksilvers have an additional +12V post going to one of the screw holes on the card. You need to make arrangements to get 12V to this location.
Finally, this won't apply in your specific circumstances, but it's worth mentioning that not all Sawtooth logic boards will work with dual processors.
Heck, not too long ago I put a 466mhz processor from a DA into a Quicksilver. It was a very "weird" set of circumstances, but basically I had a working QS, a dead DA, and a multi-thousand dollar scientific instrument that for whatever reason isn't completely compatible with a 7450 series CPU all in front of me. I suggested the processor swap, and won't repeat the stream of obscenities the owner of all this stuff said(in a good way) when we booted it up and everything worked.
Sonnets are always a solid choice for an upgrade. They also are generally "smart" enough to detect the bus speed and run at their rated frequency regardless.
There's one last word of caution on upgrades-if your current CPU is a single(most GigEs were dual) you MUST get a dual processor heatsink. It's best to have the matching one for the processor, and these can sometimes be as expensive as the processor itself. Also, all Quicksilvers, the dual processor DA, and the faster DAs had a fan essentially on the heatsink. The fan draws air from the vents in the back of the computer and blows over the heatsink. Even with that, I can tell you that a dual 1ghz Quicksilver gets quite toasty. I used an upgraded one for a while, and am currently using a factory one(there's a weird L3 cache lock-out on lower end QS logic boards).
