On 10/10/17 01:24, Rick Bensene via cctalk wrote:
Al K. wrote:
there are two versions. the 1981 8560 uses microp 1200, later ones have xebec
1410 and are sasi
070-3899-00_8560_MSDU_Installation_Guide_Nov81.pdf
070-4759-00_8560_8561_8562_Service_Mar84.pdf
If the 8560 in question uses the 8" hard disk drive from Micropolis, then
Bitsavers also has the documentation for the drive, which is the same document I
used years ago to build the hardware interface and write the code to talk to the
drive:
http://bitsavers.org/pdf/micropolis/100292_Specification_1220_Series_Rigid_Disk_Drive_Subsystems_Oct79.pdf
Thanks for the link. This could help me to devise an adapter to connect
something to the external port. But I'm not really a hardware guy.
There is a jumper block on the 1220's controller board that configures the
sector size. This wasn't documented in the above documentation. I needed 512
byte sectors, and the drive didn't seem to be responding that way (it turned
out it was configured for 1K-byte sector size), and I had to use the schematics
for the drive to figure out how to wire up a jumper block that would
reconfigure it for 512 byte sectors. And yes, I could have written the driver
to deal with this, but I didn't have a lot of memory available for the sector
buffer, so I decided to try to figure out how to reset the sector size to 512
bytes. The problem is, I can't find the schematic anywhere for the Micropolis
1220 controller board. That schematic holds the key to wiring the jumper block
for the sector size. The original jumper block was encapsulated in epoxy.
I don't remember what sector size TNIX (the Unix kernel that ran on the 8560's
CPU (which was a PDP 11/23)), but if the drive is working well enough, you
should be able to figure out the sector size being used. If you found another
drive that had the controller, you could just remove the controller board, and
daisy chain the drive in, and it'd end up using whatever sector size the
controller board on the internal drive is configured for.
Hmm, I guess I won't find another such drive anytime soon....
For some time I had an 8560 that I tinkered with for a while. It was one with the
Micropolis 8" drive. I bought it at the Tek Country store for pretty
cheap...power supply was kind of sick, so I fixed it, and got it running.
Fortunately, no one changed the root password from the default, so I could login to
it. I found TNIX to be painfully slow, as I was used to using BSD on a VAX.
Someone at Tek had done a build of RT-11 that ran on the box, and I played around
with that for a while...it was a lot faster than TNIX, but not really multi-user
like TNIX. After a while I got bored with it and ended up giving the system to
someone that I found that was really interested in it.
What were your problems with the power supply? I also suspect my
problems (hard disk resets after extended power-on time) to be power
supply related.
And, of course, inevitable question, do you still have that RT-11
version or know where it could be found?
It would not be terribly difficult to build a piece of hardware that emulated
the Micropolis drive, using some little computer (Arduino, etc.) or even a PC
through a parallel port perhaps. Using a SSD or even a USB thumb drive for
storage in it would provide lots of disk space for multiple disk images which
could be connected up to the 8560 host to appear as individual drives, and, if
the code was written reasonably well, the data transfer rate could be decent
(the drive isn't terribly fast).
I think that's my plan to continue...
If the 8560 you have is one with the Xebec SASI to ST-506 board in it and a 5
1/4" hard disk drive, then I think that the expansion port is actually SASI.
That said, though, you likely won't find many if any SCSI drives that will work
with that interface. I think, though, that the Xebec S1410 could control two
ST-506 drives. Cables might be able to be cobbled up to add a second drive to the
system (probably wouldn't fit in the chassis) off of the 1410. However, finding
good working ST-506 drives today is quite a challenge. And..you'd have to find a
drive that was compatible with the system in terms of geometry.
No. It has an 8" drive. And I got the original invoice with it, dated
from sometime in 1979. It has 8 serial ports and it later received an
11/73 upgrade, because they had memory problems in their application,
and split I/D helped them.
It would be really good, though, if somehow the original disk in your system
could be imaged at the byte level. I doubt that there are very many of the
8560's around that still run.
I received all the installation floppies for the system and the
additional tools they had. I don't know if they are complete (haven't
done a fresh installation), but I think so. I imaged all of the floppies
and posted a link to the disk images here some months ago.
Now I'd like to image the contents of the hard disk. I started a "dd"
and transferred the data over the serial line (9600 baud) with "kermit".
After some time 24h+xh the hard disk started to repeatedly reset itself.
I guess the dump was around two thirds done at this point.
regards,
chris
