Tony wrote...
Ah, but your memory is core, right? In which
case, a 'read' is actually a
write followed by a restore. Since you can read the same location and
keep on getting the same data from it (you can do that, right?), the
memory is basically working (for both read and write).
Correct, I'm aware core
does the write after read. I'm suspecting unibus
trouble but see below...
You could try writing to something else (perhaps
the data register on
your conosle termial card) to see if you can write to anything on the
Unibus. Or if you have a logic probe, you could see if the data lines
pulse low when you try writing 1's to a memory location.
I'll have to
figure out what address my console card is. I'll see if there's
any docs on bitsavers for the M7800. If I'm reading some of the paperwork
Might be listed as DL11-A through DL11-E.
correctly, whatever memory address the card is set for
corresponds to a real
core location and I'd just read/write to that specific address (DEC has a
rather odd definition of the word "register" to me) to see if the problem
changes. However, if I have a unibus problem, isn't the M7800 which is in an
SPC slot still going across the unibus? I haven't had my logic probe out in
Yes, exactly. My idea was to see if you could write to anything on the
Unibus. If you can't, then the problem is probably in the processor. If
you can, then the problem is probably in the memory.
years... I thought it blipped on pulse high not pulse
low. Surely that's
settable. I'll check :) More germane info below...
It doesn't matter. The data line is normally high, when you write a 1,
the processor brings it low, and then lets it go high again at the end of
the cycle. If your probe detects the rising edge, it'll still show
something changing (which is what you care about here).
-tony