5 Apr
2013
5 Apr
'13
12:46 p.m.
On Apr 5, 2013, at 2:31, "Arno Kletzander" <Arno_1983 at gmx.de> wrote:
Hah, a thread just in time for me!
Hello fellow collectors.
I got the card-less carcass of a pdp-11/23 (says so on the front and back type labels)
some weeks ago.
This is going to be my first pdp ever so please be a bit patient with me :)
It is the BA11 variety and contains a H9273 backplane, which as far as I could find out
is QQ-CD
(consistent with your statement below).
However the backplane has a sticker on it which is stamped "11/03" (?!)
So what kind of CPU (or more generally, kinds of boards) am I looking for to populate
this puppy?
I've already done some reading on DEC stuff from bitsavers and gleaned that in order
to make it an
11/23, it would have to hold either an M8186 (KDF11-A) or an M8189 (KDF11-B) processor.
The H9273 is perfectly compatible with an 11/23 CPU; there
is a jumper you can set for 18-bit use. Obviously, though,
turning it into a 22-bit backplane is preferable.
Fortunately, that's pretty easy.
As the M8186 only comes in a dual slot form factor, it
clearly can't make use of the CD
interconnect on the backplane. The M8189 is a quad-width board, but with the CD part
configured
for a serpentine backplane (the manual mentions two jumpers to be removed when using in
another
environment to avoid shorting signals together), so again no "meaningful" use
of the CD lanes.
Correct. The Qbus PDP-11s only used the CD lane for PMI
(or custom logic, if you had that). I'd get the M8189 if you
can, because it saves you the hassle of finding boot ROM
and serial cards for the console.
What are these intended for anyway (I was thinking of
some sort of PMI predecessor, probably
wrong by now), and what boards do I need to take advantage of them in this machine?
For an 11/23, those lanes will just go unused. It's not
so bad, really; you have to try pretty hard to fill up 9
slots.
Also, are there any ressources online about the Q-22
upgrade? I might need do do that because I
already was promised a 512kw MOS memory board by another German collector.
The 11/23 processor manual will tell you which pins
are BDAL18:21. You just need to bus those together.
The H9273 doesn't have wire wrap stakes out the back,
so you'll have to solder, but it's not very hard at all. If it's in
a box labelled 11/23, though, check to make sure someone
hasn't already performed the modification.
- Dave