Excerpt of message (sent 18 September 2009) by Kari Uusim ki:
Andrew, have you tried other ST506 disks than RD53 or RD54? IIRC none of
the RD disks were DEC built disks, but relabeled ones from other
vendors.
That's true, but I think at least in some cases (and, perhaps, on some
systems, like a Pro) they required non-standard jumper configurations.
Also possibly low level formatting, which might require tools that
aren't easily available.
paul