PDP-11/34a hung bus problem.

Mattis Lind mattislind at gmail.com
Thu May 19 09:30:25 CDT 2016

2016-05-19 7:53 GMT+02:00 E. Groenenberg <ed at groenenberg.net>:

> On Thu, May 19, 2016 02:33, Noel Chiappa wrote:
> >     > From: Ed Groenenberg
> >
> >     > After hooking up the PMK05 to the unibus, the machine was powered
> up
> >     > with the memory card, and the 'NPG' led was on.
> >
> > Oh, that's truly wierd. Most memory cards don't even connect to any of
> the
> > bus request/grant lines - they often have short loopbacks from each
> 'grant
> > in' pin to 'grant out' - not sure about NPG because canonically, that is
> > jumpered through on the backplane.
> >
> > A couple of things to check: First, does that memory even have traces
> > connected to the NPR/NPG-in/NPG-out pins? Second, does a different, known
> > working card, provoke any problems in that slot? (E.g. your serial
> > interface
> > card?) I'm wondering if the problem is the slot, not the card.
> >
> >       Noel
> >
> Yes, it does indeed to appear as weird.
> The memory card has a trace to continue the NPR line (like the little
> wire on the backplane). The card should be okay as it was the original
> card.
> I changed it for another meory cards (same type), and it has the same
> problem. I can indeed put the memory card in slot 5 and move the DL11 to
> slot 4 and see if still allows me to send a character to it (with or
> without
> the memory in place).
> I wish I had the documentation of the PMK05, the 2 sheets I have are just
> a snippet of information.
> Ed
Since you have a 11/34 I guess that you have a programmer's console (you
maybe mentioned it earlier on). What I did when checking out a 11/04 was to
follow this nice article by Jörg Hoppe:
http://www.retrocmp.com/tools/pdp-1134-programmers-console . Use the M7859
and console only on the bus, just to minimise the number of devices on the
bus that could cause trouble.

In maintenance mode you could check the memory and serial ports etc stand
alone, moving them between different slots etc.


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