Further 11/40 unibus questions...

[Johnny Billquist]

Catching up here, so it might be that this have been sorted out in later 
mails...

Josh Dersch <derschjo at mail.msu.edu> wrote:

> Ok, finally stopped being distracted by other shiny objects for long 
> enough to do some more fiddling with the 11/40.
> 
> And of course, instead of hooking up the logic analyzer, I decided to 
> play around with the Console SLU/LTC board.  Because I evidently don't 
> follow suggestions well. 
> 
> But this has a good ending, sort of.  Maybe.
> 
> So the SLU was unresponsive no matter what I did.  Tried it at 9600 
> baud, no go.  Dialed it down to 300, no dice.  Checked the continuity of 
> the dip switches, of which there are approximately 500.  No problems 
> there.  Checked, and double-checked the wiring on the serial cable I 
> built.  No go.   Stole the cable from my 8/e... still no good.
> 
> So I moved it out of the 9th slot on the processor backplane and into 
> the first slot on Unibus backplane.  (And put a grant card in the 9th 
> slot...) And hey, it works.  Toggled in a short "echo" program and what 
> I type on the terminal keyboard is echoed back, at a blistering 300 baud.

Excellent!

> So... clearly there's something wrong with the SPC slot on the processor 
> backplane.  A couple more questions:
> 
> 1) Is the NPG grant on the unibus slot on the processor backplane (slot 
> 9) supposed to be connected to the NPG grants on the Unibus expansion?  
> That is -- right now if I set my DMM to continuity mode and put one 
> probe on CA1 on the first slot of the unibus expansion, and the other on 
> CB1 on the last slot of the unibus expansion, since all NPG grant 
> jumpers are in place, the DMM shows the circuit as closed.  This is as 
> I'd expect.  However, if I move the probe from CA1 on the first slot of 
> the expansion to CA1 on slot 9 of the processor backplane, the circuit 
> is then open.  I'm guessing this is not correct.  (There is currently an 
> NPG jumper installed on slot 9.)

Are you *sure* slot 9 in the processor backplane really is a Unibus 
slot??? More correctly stated: the unibus out in the backplane A and B 
don't neccesarily imply that C-F is a Unibus SPC slot.
I haven't checked the 11/40 drawings or manuals, and I assume you have 
been reading them some. Please check this.
It's a big mistake to just assume that one slot is like another...

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol