[quoted out of the middle of paragraph]

> I was convinced to try a recent Tyan board that has some AMD parts, and some
> VIA parts, and it looks like it's a lot better; they may only suck at some
> parts of this, [....]

For what it's worth, where I work we've had lots of flavors of AMD mobos,
and here's what I've found:

KT133:	works OK if you have a BIOS update that works around the
	IDE corruption issues (Asus A7V + BIOS 1007 or later).
	We have at least a hundred of these running NetBSD.

KT133A: avoid at all costs.
	I've never gotten any of them to work right and not corrupt data.
	(Asus A7V133 is what we've had.)

AMD761+VIA686B (combo chipset):
	This is my home box, and it works just fine and dandy, no problems.
	(FIC AD11)

KT266:	my cow orker has one of these for his main box, and he
	reports no problems. (Asus A7V233)

For the corruptastic mobos, disabling all IDE DMA may help a little, but
your performance will probably suck hard - and you may still get data
corruption. Also, the mobo manufacturers are almost certainly not going
to be any help whatsoever. (Asus certainly wasn't.)