Fascinating, thanks to Pierre-Michel's analysis of his system I was able to 
ascertain there wasn't anything wrong with my BA440 at all!

The KA660 CPU brings the DSSI bus out to the C/D connector fingers and the 
CPU I had in the box was a KA640 which does not. Once I knew what should 
work, I reassembled the system and discovered that the DSSI drive in the 
rack was completely into the backplane! Youch! Anyway, all is well, I 
reseated/rebooted and now the DSSI drive is just fine and I'm busily 
installing VMS to verify the drive's integrity. (I've not NetBSD installed 
on a scsi disk that hangs off the Q-Bus.

--Chuck