PDP-10 (was Re: EDSAC on your desk.)

From: Huw Davies <H.Davies_at_latrobe.edu.au>
Date: Tue Sep 22 23:14:27 1998

At 03:23 AM 23-09-98 +0100, Tony Duell wrote:

>I have never found module-swapping to be a reliable or useful method of
>fault tracing or repair!. I find it a lot easier to look at signals on
>the 'scope/analyser and track down the real fault. I do that on _all_ the
>machines I own...
>
>You're going to have to convince me that there's something _very
>differnt_ about a PDP10 to convince me that spare modules are essential.

Well I've only tried to maintain VAX8800s, where tracing signals is not at
all possible. You cannot run the machine with the doors open for example.
(I know that you can disable the door interlocks, but after a reasonably
short period of running either the airflow sensors will shut the system
down, or core temperatures will exceed threshold and it'll go down). Of
course, with a multi-layer PC board, you can't reliably follow signal paths
anyway....

As far as the -10 is concerned, there would be several hundred (if not
thousands) of modules and the backplane (for want of a better word) was a
machine wrapped nest of identical (yellow) wires. I doubt that you could
reliably follow a signal within a rack, let alone across the whole machine.
However, as I said before, I've never attacked a -10 with a scope so I
can't be sure that this isn't possible.

 Huw Davies | e-mail: Huw.Davies_at_latrobe.edu.au
 Information Technology Services | Phone: +61 3 9479 1550 Fax: +61 3 9479
1999
 La Trobe University | "If God had wanted soccer played in the
 Melbourne Australia 3083 | air, the sky would be painted green"
Received on Tue Sep 22 1998 - 23:14:27 BST