8 Aug
2012
8 Aug
'12
11:09 a.m.
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 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.
-tony
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 ...]