<< You CAN mix PC100 and PC133 (or PC66)on the same board.
The only limitation is that if your board is set to 100mhz, your PC133 memory will only operate at 100Mhz. If you're buying memory, I would always recommend buying PC133 as the difference in price is negligable and the PC133 can be used in a new(ish) machine should you ever decide to upgrade. Stick in a PC100 chip and you might as well say goodbye to ever using it again. Yes it will work in a new system, but you wouldn't want to put it in a 1.33Gig 266Mhz Tbird would you? >>
CotswoldCS
No, I have 256 mb of PC133 cas2 for my rig. The machine I'm talking about is the parents' casino game machine(we all have one of those to take care of, don't we?)