6 Feb
2009
6 Feb
'09
1:54 p.m.
PDP 8e - Has a difficult to trace hardware problem=20
It was running but now I can't toggle in a test proigram.
Set address -> DEP -> Set Data - > DEP (Increments the
address ok)
Go back and examine memory =3D nothing.
System has four x 4K core memory.=20
Removing any one or three out of four makes no difference.
I'm rusty on PDP8's ( I last worked on one in 1972)
Help!!!!!!!!!!!!!
Why do you say this fault is hard to trace? Have you tried to track it
down (and if so, what did you find)?
In general, faults that 'stay put' are a lot easier to find that
intermittants, which have the 'interesting' habit of vinishign as soon as
the 'scope or logic analyser is next ot the machine :-)
Anyway, it's been some time since I've worked on the 8/e, althogh I know
whre the maintenance manuals are if you want me to figure things out. But
with a fualt like this, I think I'd start by looking at the Omnibus lines
-- is the CPU outputinng an address, data, and the appropriate control
lines? If not (and the fact that none of your memory works would seem to
indicate a CPU fault), then work backewards from the incorrect/missing
bus signal.
-tony