Some Progress on -8/m Mem problems

From: Zane H. Healy <>
Date: Thu Nov 25 13:54:35 1999

>>> >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

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 H. Healy | UNIX Systems Adminstrator |
| (primary) | Linux Enthusiast |
| (alternate) | Classic Computer Collector |
| Empire of the Petal Throne and Traveller Role Playing, |
| and Zane's Computer Museum. |
| |
Received on Thu Nov 25 1999 - 13:54:35 GMT

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