Why not try adding a PCI IDE adapter? It will have it's own BIOS that
will over-ride the internal BIOS.
You can even add a PCI SATA adapter for that matter.
Computer Geeks have them pretty cheap.
IF your 486 Board has PCI Slots. I know I have an ISA IDE Adapter from
Future Domain here that I've never used, but I don't know if it's going
to work any better with newer drives.
Al