Craig —
Yes, there are all kinds of hardware compatibility issues that come
up when you start running stuff at 20 mhz. The general rule is still,
"Try before you buy." I was one of the early experimenters who discovered
that there were indeed some significant problems with certain graphics
cards in fast 80386-based machines, i.e. they flat out didn't work. Most
of those problems have been solved, but it still pays to ask.
— Brad
..