M7264 Troubleshooting

Mister PDP vintagecomputersmn at gmail.com
Mon May 27 12:47:28 CDT 2019

I took a look at all the lines you mentioned. BDAL3-13, BDIN, BSYNC, and
BBS7 are all active and jump around in some manner. BRPLY is still the only
line that does not have any activity on it. None of the BDAL lines seem
shorted to ground or to each other. My DLV11-J is configured to essentially
factory settings (J3 set as console, 8 bits no parity) except for the fact
that J3 is at 9.6k baud instead of 300, the address jumpers are exactly the
same as the one you provided.

On Sun, May 26, 2019 at 6:35 PM Noel Chiappa <jnc at mercury.lcs.mit.edu>

> Hey, I owe you replies to about a zillion emails; been busy, I'll
> try and get to them tomorrow. A few quick things:
>     > My M8043 (DLV11-J) just arrived today.
> Here are the jumpers on mine, which I just pulled from a working system,
> so you can compare and make sure you have them correct:
>  A5     L
>  A9     L
>  A12    C
>  A10    C
>  A11    C
>  A8     C
>  C2     C
>  C1     C
> Key:    L = jumper from left post to right (component side up, gold pads
>                 at bottom)
>         C = jumper from center post to right
>  A6     I
>  A7     R
> I = Insert, R = Remove
>  B-X-H  X-H
> I have left out the vectors jumpers, since ODT doesn't use interrupts, and
> the line config jumpers (their setting shouldn't have any effect on the
> ability of the board to respond to ODT).
>     > I have a hard time imagining that both my M8017 and my M8043 are
>     > bad, but it could still be possible.
> Well, I did mention that the CPU board could have a fault causing it to
> put out a bad address for the console; the other likely cause is that
> both consoles are bad. Not sure which is the most likely.
> The blunt hammer debugging technique is to look at the address being put
> out on the bus; you'll need to look at BDAL3-12 and BBS7 (sort of an AND
> of all the high address bits, so devices should work on Q16, Q18 and Q22;
> in fact, the manual says that device should look at BBS7, and hot BDA13
> and up). Best to use a 'scope so you can see what the waveforms look like.
> This is slow and painful, but will allow precise, definitive diagnosis.
> If the address is good, look also at BDIN. If that's toggling, it's the
> consoles. Otherwise, CPU issue,which we'll delve into once the data
> points definitively.
>         Noel

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