Magnetic Peripherals BZ9A7A SMD disk?

[navoceano at oacis.span.nasa.gov]

Still flush with the success of interfacing a surplus Fujitsu M2284K SMD
disk to one of our Sun 3/280's, I decided to go out in search of really
big game.  In our warehouse (shades of Indiana Jones) I located a raft of
surplus Magnetic Peripherals Inc. (aka Segate) mod BZ9A7A 160 Mbyte SMD
disks.  These were rebranded Data General mod 6160 and had come from a
recently cancelled project.

The BZ9A7A is roughly similar to the Fujitsu M2284K in size and design.
The folks at Segate told me that it is electrically similar to a CDC 9766
( Magnetic Peripherals "spun off" from CDC).  The disk has 4 14" platters.
Only 6 surfaces are used. The topmost and bottommost surfaces are unused.
There are 5 data surfaces and 1 servo surface; 11 heads total (10 data, 1
servo); 823 cylinders with 20,160 bytes per track.

We have the Data General 6160 O&M manual. This is rather specific to use
with Data General computers. I also found a CDC 9766 manual which has some
useful information; particularly about sector addressing.

There is no similar disk in the current format.dat file. I guessed at 32
sectors of 630 bytes per track and made up the following format.dat:

disk_type = "Magnetic Peripherals BZ9A7A" \
	: ctlr = XY450 : fmt_time = 4 \
	: ncyl = 821 : acyl = 2 : pcyl = 823 : nhead = 10 : nsect = 32 \
	: rpm = 3600 : bpt = 20160 : bps = 630 : drive_type = 2

When I run format:
 1. The disk "clatters" and format reports an unknown disk on xy0.
 2. I identify it as a BZ9A7A.
 3. Format tries to read the defect info.
 4. Format reports a "lost interrupt" trk0, blk0.
 5. All attempts to read, write or format the disk produce the same
    "lost interrupt" response.
 6. The disk status lights sometimes report a "no seek command det."
    This is a status report, not a fault.

If there are any SMD gurus out there, I need to figure out:
 1. Is this just a waste of everyone's time?
 2. Is the disk functioning properly?
 3. Is the format.dat correct?

I would particularly like to find a good, general discussion of format and
format.dat and getting generic SMD disks to work on a Sun.

Thanks

Donald R. Newcomb
Naval Oceanographic Office
Stennis Space Center, MS 39522
(610) 688-5998
Autovon 485-5998
navoceano at oacis.span.nasa.gov
navoceano%oacis.dnet at turner-joy.noarl.navy.mil