Bad form to follow up your own posts I know. The mystery deepens. It appears that the two RF71's were "wiped" before the system was sold. Its possible that this forced them both back to an initialization step. One possible scenario is that both were set to unit id 0, and so they fail when they are both on the same bus trying to be unit 0. Does anyone have a clear set of invariants that would be true if these disks are installed at the hardware level properly. This is what we have so far: 1) Both disks connect to a KFQSA on a ribbon cable that is terminated. 2) Their "management" ports are connected to a bulkhead on the BA213 that has three ID plugs, one labelled "1" and one labelled "0". (the third is blank) 3) The KFQSA has switch 3 set, it shows up on a Qbus scan but not on a "SHOW DEV" scan. Its CSR is -200000DC (760334) = 0000 (300) RQDX3/KDA50/RRD50/RQC25/KFQSA-DISK 4) Either drive plugged into the bulkhead at the unit 0 connector seems to work. But the other one is invisible. --Chuck At 03:14 PM 7/28/99 -0700, you wrote: