11 Jul
2009
11 Jul
'09
2:43 p.m.
Hi, All,
With the recent discussion of old PDP-11 core, I was reading over
Warren Toomey's excellent description of piecing together the most
ancient version of PDP-11 UNIX known, and dreaming of the day when I
get my PDP-11/20 restored. I am missing, to my knowledge so far, two
critical elements to getting the v1 UNIX kernel (and v2 userland)
running on real hardware - an RF-11 and a KE-11A. I was figuring I'd
have to make a hardware RF-11 emulator or tweak the code in such a way
that some other device could be made to work in its place. The KE-11A
seems to me to be a harder thing to replace with an alternative.
I've read the manual on bitsavers and know the modules it's made of,
but I was hoping to find a picture somewhere just to get a visual idea
of its compexity. I know the general design of a number of 1970-ish
DEC items, but mostly, I've treated Unibus devices as black-boxes -
Unibus goes in, Unibus comes out, and in the middle stuff happens that
does things. I guess I've been fortunate in that I've never had to do
component-level repair of devices of that era (as opposed to lots of
experience with older and newer gear). I've done lots of pre-OMNIBUS
stuff, some OMNIBUS stuff, and lots of Unibus and Qbus single-card
devices. The specific place I have little experience is with Unibus
whole-backplane-era devices. The few that I've used worked when I
plugged them in.
So I'm not ever expecting to run across a loose KE-11A in the wild, so
I have to consider what it would take to make one from scratch.
Fortunately, it's a peripheral, not a processor option, so it's not
festooned with attachments into the CPU itself (unlike, say, a PDP-8
EAE). I have lots of experience with making and debugging Unibus
peripherals (COMBOARDs, among others), so I don't find that to be an
insurmountable obstacle.
I'm nowhere close to starting any sort of construction - I'm just
hoping to find a photograph for now. Long before I'd start any sort
of KE-11A project, I'd want to find a way to power up my
three-BA11-11/20 (no authentic PSUs at the moment - those were
harvested before I got the machine) and get it running. I'm expecting
to be using XXDP and RT-11 to confirm that it works before I move on
(fortunately, it's easy to drop peripherals like an RX11 on an 11/20
so I can import test programs from floppy or papertape as I debug any
problems).
Any pointers (in addition to bitsavers) on the KE11A would be much
appreciated. I plan to tear into the changes made in simh to see how
it works from a software standpoint, but the manual does have some
good descriptions already.
Thanks for any assistance,
-ethan