Odd glitch in a PDP-8/i

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Fri Jun 25 11:37:02 1999

At 08:47 AM 6/25/99 -0700, you wrote:
>I can't seem to write into location 0 on any memory field?!?

Sure it isn't a PDP-5 ? :-) Actually if it is a PDP-5 loc 0 is either the
PC or the accumulator.

>Regardless of what I write into the location, it always reads back as
>0000.

>Thots, suggestions, comments, eek!?!

The interrupt logic does a hardware JMS (0) which writes location 0 with
the contents of the PC and then executes the next instruction. I'm guessing
that the write gate in the interrupt logic is stuck "on" so even when no
one is interrupting its gating data into location 0.

If you have the prints for it this is where I would start looking.

--Chuck
Received on Fri Jun 25 1999 - 11:37:02 BST