I have a homebuilt system that automatically (continuously) reboots whenever I have more than one IDE device connected to the mobo. Doesn't matter if I use IDE1 or IDE2 and doesn't matter which two devices are connected or in which order. I've tested different IDE cables (ribbons), four different hard drives and two CD-ROMs. Note, however, that I can boot with one HD and one CD-ROM as long as there is no CD in the CD-ROM (i.e., once I put in a CD and begins to read, it reboots) so I can get into XP with one HD but nothing else. Two or more HDs produces the same result. From a fresh boot w/2+ devices, the reboot occurs just before entering the O/S (i.e. XP). Safe mode and other trouble-shooting boot options don't help. I've also tried different BIOS configurations (including basic defaults and DMA switching) and have tried repairing and completely re-installing the O/S ...same result. Also, no new BIOS upgrades available and disabling automatic restart doesn't help either. Capacitors on the mobo seem fine (i.e., none are bulged). Have thought about introducing a controller card to eliminate the mobo-direct IDE connections, but not ready to go there yet (unless necessary).
Good idea. Would it be the same (test wise) to connect power to multiple IDE devices but have only one connected via IDE cable? ...or do the devices not draw power when disconnected from the motherboard?