I just received a Dual-867 "Wind Tunnel" unit (yes, the fan cycles every few minutes). I moved a two-channel ATA/133 card from an older B&W to this new unit with a 120GB WD drive connected to it. While I had the unit open, I decided to add another 60GB (WD600) drive to the main (100MHz) bus, leaving the 66MHz bus empty.
When I booted, the 120GB and the "Macintosh HD" (60GB Seagate with which it shipped) showed up and worked fine. The 60GB WD drive (fresh from the factory) needed to be initialized. When I did so using Disk Utility, the 120GB drive disappeared! No utility (in OSX nor OS9) could see it.
On a hunch ("dumb luck"), I moved the cable connecting the 120GB to the ATA card from the "front" connector to the other channel (nearest the rear of the Mac). Upon booting, the drive was there and works just fine.
I don't know if there's some kind of conflict with this particular card (the SIIG ATA/133 for the Mac) and Jaguar or the fact that there are three ATA busses on this m'board (100, 66, 33MHz for CDs). In any case, the problem is resolved and everything works.
Mac OS X Hints