If you just have one subsystem ID, DMI might be a good
idea. I suggested
not to use the IDE controller for the second subsystem ID, as it varies
with AHCI/RAID/whatsoever modes, but this board is so old, it has
nothing of them. I suggest to use the IDE PCI ID with subsystem as
second device and drop the DMI.
Yes in fact the only settings you can change in the bios are related
to UDMA modes and such.
And btw, I was wrong on iRC - all USB controllers can be disabled.
Attached patch updated as suggested & tested.