Further 11/40 unibus questions...

[Henk Gooijen]

> Date: Sun, 31 May 2009 20:39:26 -0700
> From: derschjo at mail.msu.edu
> To:
> Subject: Further 11/40 unibus questions...
>
> Hi all --
>
> Still having trouble with my 11/40, though it's getting closer.
>
> Currently the issue is:
>
> Without a unibus terminator installed, the machine seems to function in
> that I can use the front panel, toggle in and run short programs, etc.
>
> With a unibus terminator installed, the front panel is _almost_
> unresponsive -- I cannot examine or deposit memory or load addresses.
> Toggling "Run" causes a brief flicker of activity (the "Run," "Proc,"
> and "Bus" lights come on, the data lights flicker, and then they turn
> off, and the "Console" light comes back on.).
>
> Ian lent me his M9300 terminator, which caused no changes in behavior.
> So at least I can (probably) rule out a faulty terminator.
>
> I've verified that grant continuity cards (the tiny annoying ones) are
> installed in slot D of all empty Unibus slots, and that the NPG jumper
> is installed in all slots (since I currently have no DMA devices installed).
>
> Question: Should the NPG jumper _also_ be installed in the one SPC
> Unibus slot on the processor backplane? (I have a console SLU installed
> there currently.) This does not currently appear to be present.
>
> Before I break out the logic analyzer this evening and start debugging
> Unibus termination signals, I just wanted to make sure my current
> configuration seems sane.
>
> The boards are installed as follows:
>
> Rear:
>
> Slot 4 : Empty M9300
> Slot 3 : Empty
> Slot 2 : M7891
> Slot 1 : Empty | M981
> ---
> Slot 9 : M7856 | M981
> Slots 1-8: 
>
> Front:
>
> (As mentioned before, all "empty" unibus slots have a unibus grant card
> + NPG jumper installed, Slot 3 has the NPG jumper installed.)
>
> Thanks once again,
> Josh

The machine seems to do something (for a short while that is).
The only thing I can say is what I have encountered. I was triggered
when you wrote that you have the M7856 in slot 9 ... make sure that the
CA1-CB1 (NPG) pins are wired together on the backplane!  The M7856 is
one of the modules that does not use NPG, but also does NOT connect the
two pins on the module! I have that written on my webpage www.pdp-11.nl
(peripheral - comm - interface modules - DL11-W).
 
I remember that I soldered a wire on the module to connect those two pins,
as I did not want to mess with the backplane ... If you do so, make sure
that no flux and tin gets on the contact fingers!

- Henk.