2 Apr
2008
2 Apr
'08
3:07 p.m.
A year and a half ago I was playing with a PDP-8/e and
trying to get an
EAE working with it. I ended up needing a later version M8330. My
original boards were rev 1 and the EAE didn't work until about rev 3.
The drawings I found online were WAY different than the boards I had.
For the EAE, it looked like there were some serious timing issues, so
the later board revisions were quite significant.
So, if your boards don't match the drawing rev, don't expect there to be
a match.
This issue is by no means limited to the PDP8/e, or indeed DEC.
On the 11/45, there was a amjor change to one of the boards which added
an extra latch on some signals, and needed a backplane mod (an extra
clock signal) for it to work. Please don't ask how I found that ont...
And HP did similar things. On the HP11205 for example (RS232 interface
for the 98x0 machines), there were major changes betwee Rev A and later
veriosn. The latter had a little modification to get it to work in the
9830, and extra circutiry added to generate a delay after a carriage
return. The 2 boards are nowhere near the same! (I have something I call
an 'A.5'. I've don the 9830 mod, just a cut trace and jumper, but not
tried to add the delay circutiry).
-tony