M7264 Troubleshooting

Noel Chiappa jnc at mercury.lcs.mit.edu
Wed May 22 07:28:31 CDT 2019

    > From: Glen Slick

    > According to the M7270 LSI-11/2 Microcomputer Module User's Guid[e],
    > it uses BC1, BD1, BE1, BF1 for SCLK3 H, SWMIB18 H, SWMIB19 H, SWMIB20 H.

Oh, thanks! I wonder how I missed that, looking at the prints? (The
drawings have these nice dark arrowheads to indicate backplane
connections.) I just visually blew past it, I guess.

BH1 is also used there (for SWMIB21 H); and on the previous page, the STOP L
output is on AE1, and MTOE L (whatever that is) can be fed from AK1.

Not quite sure how a Q22 memory card causes the problem, electrically, since
those lines are inputs on the memory card, so it's an input<->input connection
(i.e. voltage sources in TTL), but obviously it does.

And I also don't see why Q18 cards are a problem; BDAL16 and 17 are
AC1 and AD1 respectively, which I don't see in the 'extra pins' list
for the LSI-11/2. Oh well, not too important to track it down.

Thanks again for catching my miss! Wow, it's been a loooong time since
I worked with an LSI-11 - about 40 years! :-)


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