For example.
Put the logic probe on MD0 (MSB) on the backplane and
deposit 7777. It blips low, right? Now examine that location (assumed to
be a 'working' location) -- it blips low again.
Now look at MD11 (LSB) and do the same things.
All 12 lines of the MD Bus look to be functioning both ways. This was
tested with the proper voltage hooked up to the probe.
Well, if all 12 data lines are doing the same thing when you deposit and
examine 7777, then the memory may well be working, and the problem may be
on the CPU boards. I will have a look at the prints and tech manual when
I have a few minutes.
I might not have been totally clear here, when the data goes one direction,
it sets the line high, when it goes the other direction it sets it low. Or
should it be doing something else?
Hope to be able to get back at this tomorrow night, or first thing this
morning.
OK, I started thinking about this last night when I should have been
sleeping :^) So I decided I'd better do some more checking. First I've
decided I appear to be backwords, let me guess on the front panel the MSB
is '11'? I was really getting confused/worried till I realized that
apparently I'm reversing things again.
OK, if I load a specific address, and deposit 7777 blips low, when I load
that address and examine it, it goes high. It doesn't seem to matter what
bit I'm checking (MD0-MD11).
However, when I fill a whole address range with 7777, and start examining
it, I get 'pulses' on MD4-MD11, but not on MD0-MD3. Note, this obviously
isn't happening on xxx0-xxx3 since that's not fixed.
Tonite I should be able to start checking the G104 board.
Zane
| Zane H. Healy | UNIX Systems Adminstrator |
| healyzh(a)aracnet.com (primary) | Linux Enthusiast |
| healyzh(a)holonet.net (alternate) | Classic Computer Collector |
+----------------------------------+----------------------------+
| Empire of the Petal Throne and Traveller Role Playing, |
| and Zane's Computer Museum. |
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http://www.aracnet.com/~healyzh/ |