8 Aug
2012
8 Aug
'12
7:16 p.m.
On 2012-08-08 23:17, ard at p850ug1.demon.co.uk (Tony Duell) wrote:
It is rather convenient. But it should be pointed out that DIP switches
for the NPG signal only exists for the first eight Unibus slots, which
are in the first backplane. If you put in any more Unibus backplanes,
it's the same standard story of the jumpers on the pins as always.
(I *think* it is eight slots on the first backplane in the 11/84, but I
might remember that detail wrong, but I hope people understand the idea
even if I happened to get the actual number wrong.)
>
>From: "Tony Duell"<ard at p850ug1.demon.co.uk>
>Sent: Tuesday, August 07, 2012 9:16 PM
>To:<cctalk at classiccmp.org>
>Subject: Re: Odd PDP-11/84 Unibus behaviour
>
>> > >>
>> > >>I'm noticing something on my PDP-11/84 that I can't explain.
I've
> > >
> > >I';ll try a one-word explamation : 'Grants'.
> > >
> > >[... snip excellent explanation from Tony ...]
>
>I remember working on grants in the 11/84.
>The 11/84 is very user-friendly, because there is a board next to
>the CPU that has several DIP switches. Each DIP switch opens
>or closes the NPR of one slot. So there is no need to count pins
>on the backplane to find CA1-CB1. Just open/close the switch
>for the appropriate slot.
Right. That I did not know. TO be honest, the
J11-based machiens are too
mdoern for my taste:-) However, I would adcvise against flipping said
switches unless you know
what you are doing (for example you'bve got a switch open correspodning
to an empty slot). It is better, IMHO, to actuall trace the fault and be
sure it is an NPG problem before changing anything. Otherwise you will
get in a muddle very quickly.
Right. Random flipping of switches is no way to troubleshooting.
Johnny