Some personal experience...
I ordered a P3 800 100FSB/Slot 1 from Onvia over the weekend, and it arrived this morning. I just dropped it into my Soyo 6ba IV+, and have spent the past half hour testing various combinations.
Right now, I have it at 976 Mhz, with the FSB at 122. I've had to step the voltage up 5%. Motherboard Monitor reports the voltage as 1.71 v. I'm going to leave there for a burnin, and then see if I can drop it to +2.5%, or back to the default voltage. I tried 124 FSB = 992 Mhz, and had to step the voltage up to +7.5% to get into Win 98SE, only to have it crash shortly thereafter. So I dropped back to 122/976. I'll keep it here for now, while I do some stability testing.
So, I have 976 Mhz, using a Slot 1 with retail cooling. I'm kind of lazy, never having gotten into esoteric or do it yourself cooling solutions. I do have a Tornado 1000 case, though, with pretty good ventilation.
I'm happy (so far). I went with the 800, rather than a 700, hoping that the higher multiplier would help me get close to the gigahertz mark without having to push the FSB to 133.
Now for a video card upgrade. (The present video card is a Voodoo3 2000 PCI.)
-Baz