Hanging, Halting and Continuing

[jbray%bbn-unix at sri-unix.UUCP]

From:  James Bray <jbray at bbn-unix>

It seems to me that the real point is being steadily overlooked in this
discussion. I forget whether I   my original response to the list or not,
so I will say again: it sounds like the machine is getting hung in a tight
loop somewhere waiting for something that it is sure is going to happen which
isn't happening. For example: once, at my last company, we had an intermittent
problem with our Perkin-Elmer 3220 the symptoms of which were that it would
hang in the boot on a Sense-Status instruction waiting for the disk. Vinnie,
the field-service guy (and a good one) never did figure it out. He eventually
did something that shouldn't have had any effect, but it went away. We agreed
that it was a (dread) backplane problem. 
  If you halted the machine under these circumstances, you would see that it
was executing either the sense-status instruction or the immediately-following
branch. What was happening was pretty obvious: it was a hardware problem, and
needed to be fixed.
  So: whether you continue your machine or reboot it would seem to be a rather
secondary consideration. The important thing would seem to be to get the PC and
other context, find out what is going on, and fix it. 
--Jim Bray

P.S. I attempted to send this out the other day, but a bunch of weirdness
resulted and I don't think it made it (I didn't get a copy back). Apologies
to those who get multiple copies.