PDP-11/44 CPU Configuration

From: CLASSICCMP_at_trailing-edge.COM <(CLASSICCMP_at_trailing-edge.COM)>
Date: Wed Apr 21 10:44:04 1999

>> Speaking from decades of experience, you *do not* put a Unibus machine
>> together in a big configuration, especially from mix-and-match used
>> parts, and get it to work. You go down to the most basic configuration
>> possible, and then add parts one at a time, testing as you go.

>Well, with the exception of the DELUA, and RAM everything is configured the
>way it was when I got the machine, but that's a good point.

I hope nobody takes it as an insult when I try to encourage them to take
a system down to its bare-bones and build it back up step-by-step, but
this really is the best way to debug a system that one knows little
about the history of. Just because something is written on the sticker
on the cover of a system about its configuration doesn't mean that it
was working in that last configuration! In particular, with Unibus
machines you have to check the presence of the NPG jumpers on the backplane
if you have the slightest reason to believe that the configuration has
been meddled with in the slightest since it last worked. A single
mis-placed jumper anywhere in the system can cause the entire system
to lock up when the first DMA attempt is made...

Tim.
Received on Wed Apr 21 1999 - 10:44:04 BST