19 Oct
2006
19 Oct
'06
12:59 p.m.
Quoth Jay West, in part:
The memory address test program fails though. It halts
at 246 indicating a
memory addressing error. R1 points to 422. Examining memory via the front
panel shows the following:
[...]
So it looks to me like it is able to store 420 in 420,
but nothing after
that. I would normally think there is a problem with the memory board
(M7891). However, I have replaced that board with 2 others, and all 3 boards
fail at the same address AND with the same values. I find that likely to
rule out the memory board as really being bad. In addition, I can deposit
and examine values to locations 420 through 430 via the front panel just
fine. It's my understanding that the KY11-LB puts data in memory via the
unibus, so I would think this makes it somewhat unlikely to be a backplane
issue. Is it a strong likelyhood that the problem is the cpu set itself
then, as that's what would be writing the values to memory during the
address test?
It sounds like you've already done a good job of eliminating the obvious
hardware issues. :) The fact that the data is _inverted_ afterwards
interests me; that sounds like the sort of complememt-memory test pattern
a memory test program would use in alternation with the first. So I
wonder:
Is the memory-test program corrupted?
If so, is the source you loaded the test from bad, or did the test load
correctly and later get partially corrupted in memory?
If it got corrupted in memory, can you reload it and get it corrupted
again? :) More to the point, would it re-corrupt in a consistent manner?
...That's just what pops to my mind, anyway. It seems like it'd be easier
to have a fault that corrupted the test program than a fault that produced
such peculiar and far-reaching results. :)
-O.-