failure for M217A test on all three of our cards -- does the test work?

Peter Peterson

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Mar 17, 2022, 5:20:05 PM3/17/22

to PDP-12 Restoration Project

Hi All -- especially Mike:

We are in the process of FCTesting all of our compatible cards just as a part of maintenance but also in the hopes of tracking down a longstanding issue with our tape drives (see our videos for more information).

The FCT (with Mike's mods and software) passes tests for M617, but when we test our three M217s (in E3, E4, and E7), they all fail like this:

So -- first -- do you know if the M217 test works correctly?

Then, I tried to use the test for the M169B and that failed to be opened by the tester.

Do you know which (or is there a list somewhere) documenting which tests currently work and which don't, etc.? (This would be a great thing to track using issues on GitHub).

Thanks,

Peter & Julian

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Peter A. H. Peterson, Ph.D. (he/him)

Assistant Professor
Department of Computer Science

University of Minnesota Duluth

Michael Thompson

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Mar 17, 2022, 5:27:06 PM3/17/22

to Peter Peterson, PDP-12 Restoration Project

If the outputs are open collector, they probably need a pullup resistor connected to the output pin. There are some pullup resistors on the tester.

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Michael Thompson

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Mar 17, 2022, 8:21:17 PM3/17/22

to Peter Peterson, PDP-12 Restoration Project

I fixed the M169B.TST test vector file, and checked it into GitHub.

Can you try it?

On Thu, Mar 17, 2022 at 5:20 PM Peter Peterson <pa...@d.umn.edu> wrote:

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Michael Thompson

Peter Peterson

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Mar 17, 2022, 10:31:47 PM3/17/22

to Michael Thompson, PDP-12 Restoration Project

Hi Mike,

Thanks very much. We will test these asap (probably tomorrow or Monday) and get back to you when we do.

Thanks again!

Peter

Peter Peterson

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Mar 21, 2022, 1:55:45 PM3/21/22

to Michael Thompson, PDP-12 Restoration Project

Hi Mike,

We ran the updated M169 test and it works! Thanks.

About the pull-up resistors... the test doesn't specify what to do, or what value resistors to use. We now see that some tests explain what P means (e.g., M71902D_2.TST says "Tolerates 3.3k ohm pullups to +5v on pin (are needed for PART 1"), but the test for M217 isn't specific, and the resistors on the board for use are not that high. We're also wondering exactly how to wire things up, since we don't want to inadvertently fry anything. We have four pins that are supposed to have pull-ups, but only one pull-up resistor.

Specifically, the M217 test identifies four P's ... we are wondering how to connect them all to the pull-up resistor on the board. It looks as if all of the open collector outputs are always high and so it would be fine to connect them to a single pullup, but we're not sure. Any advice would be appreciated!