PDP-11/34a hung bus problem.

Noel Chiappa jnc at mercury.lcs.mit.edu
Wed May 18 19:33:54 CDT 2016

    > 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.


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