M7264 Troubleshooting

[Jon Elson]

On 05/26/2019 10:44 AM, Jon Elson via cctalk wrote:
> On 05/26/2019 12:13 AM, Mister PDP via cctalk wrote:
>> Ok, small update. My M8043 (DLV11-J) just arrived today. 
>> It seemed in good
>> condition so I confirmed it was set up correctly (9.6k 
>> baud and console on
>> J3), built a serial cable from the information provided 
>> on gunkies, and put
>> it into my system. Sadly, it behaves exactly how it did 
>> with the M8017. No
>> output, no activity on the BRPLY line. I have a hard time 
>> imagining that
>> both my M8017 and my M8043 are bad, but it could still be 
>> possible.
>>
>>
> Well, if just ONE address line driver on the CPU has gone 
> bad (or a short in the backplane) it could prevent the DLV 
> from recognizing the address.  If there are any other 
> boards in the system, take them out.  Maybe even the 
> memory boards, and try to read/write the DLV addrsss from 
> the console.  (Oh, maybe that's the problem, you don't 
> have the full programmer's console on this machine.)
>
Oh, DLV means Q-bus, so there isn't much choice EXCEPT 
serial console, is there?
Yeah, when the serial console doesn't work, you've got a 
problem. You could check each addr/data line to see that it 
wiggles.  If it doesn't wiggle, then you can see if the 
state it is in makes sense. Obviously, somewhere in the 
serial console routine, it should be addressing the serial 
console, so every line should at some point be in the state 
to select the console CSR.
A logic analyzer set up to read out the bus would be a good 
tool at this point.

Jon