> | I can't explain this behaviour but to me it looks like some of the 
> | informations RQDX3 stores on the surface of the disk were corrupted 
> | and thus the combination RQDX3/RD53 was in trouble. Erasing all the 
> | information from the disk-surface via BIOS/DOS forced the RQDX3 to 
> | completely reinitialize the disk ...
> 
> We call using a PC to scrub a DEC disk the last resort.  Since I'm not
> aware of any DEC utility that allows me to provide the original
> manufacturer's defect list you're living on borrowed time.  The data
>...

A much better way to reformat RD53's and RD54's is to do the formatting
on a PDP-11 using the XXDP+ diagnostics, or to just use the built
in formatter in a Vaxstation 2000.  The XXDP+ and VS2000 formatters
are much more robust than the formatter that runs on a Microvax.

An excellent source of information on the RD-series disks and the
RQDXn controllers is the file

   THIRD-PARTY-DISKS.TXT

available via anonymous ftp from the home anonymous directory of

   ftp.spc.edu

(i.e. in the [ANONYMOUS] directory.  Some web-browser's ftp facilities don't
like non-Unix like paths and may not fetch this file for you, but you can
always just use ftp.)

You'll find all sorts of information on the hardware, including arcania such
as:

1.  Many BA23's have power harnesses that may burst into flames if you
    try to power more than 1 disk at a time.

2.  The jumper settings necessary to get third-party (non-DEC) MFM disks
    to work with DEC controllers.

As long as we're talking about hardware, another excellent on-line source
of trivia on Q-bus and Unibus hardware is the anonymous ftp site

   sunsite.unc.edu

in these directories:

   /pub/academic/computer-science/history/pdp-11/hardware
   /pub/academic/computer-science/history/pdp-11/decusdocs
   /pub/academic/computer-science/history/pdp-11/decusdocs/vs0114
   /pub/academic/computer-science/history/pdp-11/decusdocs/vs0121

Tim. (shoppa@altair.krl.caltech.edu)
Kellogg Radiation Lab, Caltech.