ISO: Motorola MDP-1000 info/software

[Josh Dersch]

Hi all --

This is a long shot, but I was curious if anyone might have information on
the Motorola MDP-1000 minicomputer.  I picked one up recently and I'm
working on restoring it.  Of particular interest is the power supply, which
is external to the processor and which I am missing.  I think I have the
voltages worked out (+/-5V and +/-15V), but there are a number of other
signals on the power supply connector that I'm unsure of at the moment.

I've put a few pictures up here:

https://1drv.ms/u/s!Aqb36sqnCIfMpIVYmzKjFnsT3nHh8w?e=b2iqqv

I'll note that this isn't technically an MDP-1000 -- it's labeled as an
MDP-6650 on the rear.  I suspect that this is a ruggedized version of the
1000 intended for harsher environments.  The front panel of mine appears to
be identical to the drawings of the MDP-1000 in the manuals I have.

It also came with a binder of documentation (but alas no schematics) that
I'll be scanning soon and getting off to Al.  It's an odd little system --
5 12-bit registers, a 12-bit ALU, and a 12-bit Instruction Register, but
the memory is 8 bits wide.  Instructions are packed into two bytes
normally, but there's a special 64-byte region of memory that can be used
to store "shared bytes," which allow encoding certain instructions into a
single byte, taking the other byte from the shared region.  I've never seen
anything quite like this.  I wonder why they didn't just use 12-bit wide
memory...

Also the process for using the front panel to examine and deposit memory is
insane.  Here's the instructions for reading a memory location; it's 10
steps.  Depositing is 17.

https://1drv.ms/u/s!Aqb36sqnCIfMpIVWThgwlxgCMQo59A

If anyone has anything on this, let me know.  Not expecting much, but it's
worth a shot.
- Josh