22 Feb
2014
22 Feb
'14
3:46 a.m.
On Fri, Feb 21, 2014 at 10:08 PM, Charles
<charlesmorris800 at centurytel.net> wrote:
Another mystery board in my junk box... this one
should definitely be
for a PDP-8 because it has no signals on the F connector fingers.
And the I/O connector points towards "F" - that's characteristic of
the PDP-8/a chassis. PDP-11s have a backplane connector where the
PDP-8/a has a gap to route the cables.
I've googled all the numbers on it and can't
figure out what it's for.
It has a Z80 CPU, some RAM and ROM, and a lot of bus drivers.
That is a mystery board.
There's
an empty 40-pin socket at U1, don't know if it had another Z80 or
what.
If you see a pattern off of it of sets of 8 lines (data bus, address
bus) in the same place as a Z-80, then it's possible, but I think it's
more likely that it's a peripheral chip than another CPU. I'd start
with guessing it's a serial chip and trying some of the common ones
from the era.
http://s1181.photobucket.com/user/DrCharlesMorris/media/PDP-8/P02-21-14_205…
The output(?) connectors are unique at least to me:
http://s1181.photobucket.com/user/DrCharlesMorris/media/PDP-8/P02-21-14_205…
Looks like four pin plugs would seat in those sockets (they aren't
coaxial).
Those look like smaller versions of connectors I've seen on a Qbus
Pertec video card. Those _were_ coaxial, with tiny center conductors.
What are the chips that are directly attached to those I/O pins? You
might learn something if you can decipher the physical layer.
-ethan
