Formatting non-DEC disks using zrqch0...

The RD53 drive in my 11/73 has finally gone to silicon heaven, after a brief resurrection. Given the reputation these drives seem to have, I'm not too surprised. So a few nights ago I dug through my stacks of ancient hard drives and found three possible candidates for replacement: - A Microscribe 6085, which seems to have the same drive geometry as an RD53 - Two Seagate ST-251s, which seem to be identical to an RD32 All of these are in "unknown" condition (I haven't used them in years), but spin up without making any evil noises and are recognized by the RQDX3 controller. To the best of my recollection, all three were formerly used in PCs. I've used zrqch0 (booted via vtserver) to format all three of these disks. In all three cases the formatting appears to be successful -- the drives format for a few minutes, then go through three verification stages for another 20-30 minutes. During this time I can hear the heads being stepped, and the drive access light blinks. At the end of the format no errors are reported. I'll note that in order to do the format on these drives, I had to go through the process manually (as opposed to the "AUTOFORMAT" mode of zrqch0) -- for the Microscribe this was because zrqch0 didn't recognize the drive (showed up as "unknown"), for the ST-251s this was because the fault tables could not be read off the drives. I suspect this may have something to do with the issue I'm seeing, but of course this is pure speculation. I've tried various permutations of the formatting options, but I've had no joy there. After formatting the drives, no other utilities seem to be able to make use any of the drives -- running the disk exerciser (zrqah0) fails after the first test step (and after a very small amount of disk activity) with an error similar to the below (this varies slightly based on the test being run): FATAL I/O ERROR * DISK 0 WENT OFFLINE * SUB_CODE: NO VOLUME MOUNTED OR DRIVE DISABLED BY SWITCH * COMMAND: READ_COMPARE Interestingly, 2.11BSD's 'disklabel' is able to partition and write the label to the disk. Mkfs, however, fails with: ra(0,0,0) error op=A2 sts=23 write error 3 Exit called I've tried this with two different RQDX3 controllers with the same results (and these controllers worked fine with my RD53 until it failed). Is there a magic step I'm missing? Is what I'm attempting to do (use non-DEC drives) not possible? Any ideas or suggestions? Thanks for any help here... Josh