I have a UMAX SuperMac C600/200. It seems that it won't do slave IDE devices.
I have an IDE hard drive, and a SCSI CD-ROM. If I try to add a slave IDE hard drive or CD-ROM, it doesn't recognize them. However, if I make those devices master, and set the current IDE drive to slave, the new device works, leaving the original hard drive unusable.
Does the UMAX internal IDE socket only allow one device? I've tried things as simple as zapping the PRAM, to no avail. Incidentally, neither Drive Setup or Apple System Profiler recognize these slave devices.