PDP-11/34a hung bus problem.

E. Groenenberg ed at groenenberg.net
Thu May 19 00:53:17 CDT 2016

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
the memory in place).

I wish I had the documentation of the PMK05, the 2 sheets I have are just
a snippet of information.


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