The Adaptec cards (not surprisingly did work either).

The GXT110P is a S3TrioV64+ (375 chipset).

I tried a 325 chipset as well, no good; it was not recognised. I don't
have another V64+ card to try to see if it is the bios on the card that
makes the difference or whether it is implicitly recognised.

Time for me to press the machine into service, so that is about the end
of me playing with hardware on this box.

-Chris