KM11s and the PDP-11/20 (was Re: Help w/DEC H742 +15V...)
ethan.dicks at gmail.com
Mon Apr 13 23:55:18 CDT 2009
On Mon, Apr 13, 2009 at 10:13 PM, Josh Dersch <derschjo at mail.msu.edu> wrote:
> Ethan Dicks wrote:
>>> There's also an interesting Unibus analyzer made by Guy Sotomayor...
>> I have one of those boards, but since I got it from Guy as a bare
>> board, I still have to assemble mine...
> The KM11 looks like it may be very useful for getting my 11/40's CPU running
> again... anyone have any experiences to share using one of these?
No. I wish I did, but I got a pair of KM-11s since I have several DEC
devices which can use them (RX01, RK11-C, RK11-D, PDP-11/05,
PDP-11/20). I don't happen to have an 11/40.
The primary purpose for my KM11s, was to facilitate the restoration of
my 11/20 - it was butchered and dumped prior to me acquiring it (I
rescued it from the skip at work, already in many pieces), and to
attempt to get my RK11-C working (it arrived from the same place
intact, but is suffering from some visible corrosion on the pins of
the backplane, so I don't know if I'll ever get it working reliably).
I don't need to do much RX01 electronic repair (a new drive motor and
a new stepper motor would go a long way to returning both sides of a
dual drive to work, but the boards seem intact); however, I think it'd
be cool to watch the drive work by observing the blinkenlights.
These items are way, way down on my DEC list (I have PDP-8s to work on
first), but someday the 11/20 will bubble up to the surface. I know I
don't have all the core that originally came with it - one of my
cow-orkers souvenired it 20 years ago. I have the backplanes and the
driver boards, but am missing at least one 4K core plane. My _hope_
for this system is to get an older version of RT-11 up on it first,
then *perhaps* if I can get enough memory on it and some compatible
disk device, see if there's an ancient-enough version of UNIX in the
PUPS archive to run on it (it would have to be a version from 1971 or
1972, IIRC, to fit on a KA-11 w/16-bit address bus). I don't know
that it's possible, but it's a goal.
I'm thinking that the RK11-C might work there, or since I know it
works, the RK11-D, plus one or two RK05s. It's possible that those
are too new for PDP-11 UNIX, but for old RT-11, I can probably get
away with the SJ monitor and an RX11 w/dual RX01s.
First, though, I have a lot of reconstruction to do on the 11/20.
IIRC, I will need some PSUs to get the ball rolling, since that's what
I think was yanked from it before it was trashed. I think I have the
CPU box plus two memory boxes (the size of 3 BA-11s, essentially), but
I don't recall the PSU model number off the top of my head - it's one
that supports multiple single-height power cards in a series of
DD-11C-sized 4-slot hex-height backplanes. Oh... I probably don't
have enough M920s to reconnect everything - I don't think many of them
were in the dumpster with the CPU.
The missing parts is why I never did much with it. Maybe I'm better
off trying to recycle the front panel and drive it from something
modern. The chances of finding multiple PSUs and short Unibus
interconnects that aren't already in an 11/20 seem small these days.
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