ISO: PDP-11/40 LTC and Stack Limit options

william degnan billdegnan at
Wed Nov 23 09:11:55 CST 2016

>> Interesting.  I suppose the LTC on the M7856 could also be disabled...
> I'll have to try that and see if it works.  The DL11-W manual doesn't seem
> to cover any special installation procedures for the 11/40, and the 11/40
> System Manual describes Slot 9 as a "SMALL PERIPHERAL CONTROLLER (USUALLY
> DL11)" slot without mentioning the lack of NPG and the LTC oddity.  Weird.
> I now have the CPU passing diagnostics with flying colors (there was a
> problem with the IR Decode logic causing incorrect reserved instruction
> traps), and I can boot RT-11 from the SCSI controller, yay.  Now to track
> down the EIS and Stack Limit options...
> - Josh

Glad to hear.  Also this thread may have given me the clues I need to boot
an RL02 / 11/40 / RT-11.
1) I never thought to check to see if my system was used with a KW11-L in
the past, I too appear to have a CPU set that came from a different
system.  I need to check for a missing jumper in slot 3 of the CPU
backplane.  F03R2 and F03V2.

2)  I actually do have a KW11-L (M787), but whenever I attempt to use it I
can't do much other than toggle memory using the front panel.  Simple CPU
programs fail, and I can't boot using M9312.  (I actually tried 2 of these
cards, same result) I thus assumed I did not have a CPU backplane wired for
a KW11-L, but it could be that it actually *is* and the problem is with the
M787 card, a fault in the card.   I have 0 experience with altering or
testing backplane jumpers, but I will try.  I have always used an extender
card instead and probed signals form the extension card as a cheat.  It
seems like the NPG is OK AFAICT, but I did not check slot 9.  It does not
seem to matter whether I have a grant card in slot 9 or not either.

3) I would not mind getting something like Guy's UA11 to test with.  Are
these available?

4) I have been also working on getting a M7856 wired to 177560 so I can
emulate a TU58.  Made progress last night, will keep working on getting
XXDP running.  Up to this point I had been loading in one routine at a time
using PDPGUI.  Some success, used to learn my system was expecting a KJ11
(M737), which fortunately I had.  Since then I verified that my CPU cards
are correctly jumpered for what I have installed in the backplane.  Per
this conversation I believe I have the correct cards and enough working RAM
to operate RT-11.

Noel - Do you ever make a trip up my way?  If you ever have time to stop by
to help me with my system I'll trade you some hardware or food for  your



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