Just in case...
Don't The roms for the 600 and 1200 have ide and pcimca built-in?
could explain why the rom isn't working on the motherboard?
Don't you need the 500/2000 rom?
(and yes the 500 version had a wire you left alone or cut based on what version motherboard you had)
500/600/2000 3.1 roms are all the same and work with ide etc. early 2.05 rom(27.299) is missing ide/pcmcia support,27.300 and 27.350 had ide/pcmcia support.
all the above work in 500,600,2000
A1200 uses 2 roms,totally different from 600 roms. 1200 roms have ide/pcmcia support.
and yea,add or remove wire depending on 500 rev.
