Further 11/40 unibus questions...

[Josh Dersch]

Henk Gooijen wrote:
>> Date: Sun, 31 May 2009 20:39:26 -0700
>> From: derschjo at mail.msu.edu
>> To:
>> Subject: Further 11/40 unibus questions...
>>
>> Hi all --
>>
>> Still having trouble with my 11/40, though it's getting closer.
>>
>> Currently the issue is:
>>
>> Without a unibus terminator installed, the machine seems to function in
>> that I can use the front panel, toggle in and run short programs, etc.
>>
>> With a unibus terminator installed, the front panel is _almost_
>> unresponsive -- I cannot examine or deposit memory or load addresses.
>> Toggling "Run" causes a brief flicker of activity (the "Run," "Proc,"
>> and "Bus" lights come on, the data lights flicker, and then they turn
>> off, and the "Console" light comes back on.).
>>
>> Ian lent me his M9300 terminator, which caused no changes in behavior.
>> So at least I can (probably) rule out a faulty terminator.
>>
>> I've verified that grant continuity cards (the tiny annoying ones) are
>> installed in slot D of all empty Unibus slots, and that the NPG jumper
>> is installed in all slots (since I currently have no DMA devices installed).
>>
>> Question: Should the NPG jumper _also_ be installed in the one SPC
>> Unibus slot on the processor backplane? (I have a console SLU installed
>> there currently.) This does not currently appear to be present.
>>
>> Before I break out the logic analyzer this evening and start debugging
>> Unibus termination signals, I just wanted to make sure my current
>> configuration seems sane.
>>
>> The boards are installed as follows:
>>
>> Rear:
>>
>> Slot 4 : Empty M9300
>> Slot 3 : Empty
>> Slot 2 : M7891
>> Slot 1 : Empty | M981
>> ---
>> Slot 9 : M7856 | M981
>> Slots 1-8: 
>>
>> Front:
>>
>> (As mentioned before, all "empty" unibus slots have a unibus grant card
>> + NPG jumper installed, Slot 3 has the NPG jumper installed.)
>>
>> Thanks once again,
>> Josh
>>     
>
> The machine seems to do something (for a short while that is).
> The only thing I can say is what I have encountered. I was triggered
> when you wrote that you have the M7856 in slot 9 ... make sure that the
> CA1-CB1 (NPG) pins are wired together on the backplane!  The M7856 is
> one of the modules that does not use NPG, but also does NOT connect the
> two pins on the module! I have that written on my webpage www.pdp-11.nl
> (peripheral - comm - interface modules - DL11-W).
>  
> I remember that I soldered a wire on the module to connect those two pins,
> as I did not want to mess with the backplane ... If you do so, make sure
> that no flux and tin gets on the contact fingers!
>
> - Henk.
>  
>
>   
Thanks -- installed the NPG jumper for slot 9, no change.

Here's a question:  The M9300 Ian lent me has three jumpers, labeled as 
follows:

W1 : "Remove jumper for beginning of non processor bus termination"
W2 : "Remove jumper for end of bus termination"
W3 : "Remove jumper for end of processor bus termination"

Currently, W1 is installed, W2 and W3 are removed.  Is this correct?

I'm curious what is meant by "processor bus" vs. just "bus" in this 
context -- can someone fill me in?

Thanks,
Josh