On 11/22/16 4:00 PM, Josh Dersch wrote:
On 11/22/16 9:27 AM, Noel Chiappa wrote:
> From: Josh Dersch derschjo at gmail.com
> see if the same is true for other bus grants -- I can run the
system
> with no grant continuity card at all in slot 9 and everything
works.
Well, the BG4-BG7 grants definitely _are_ run through the SPC slot 9
(see
below) - at least, on a stock system. It's _possible_ that the software
you're loading doesn't use interrupts. (I have this vague memory
that, unlike
the -11/34, the /40 doesn't complain if there's a non-continuous
grant line.)
Or perhaps someone wired them across on that slot, to avoid
knuckle-mashing
trying to put a G727 down there.
Yes, I'd expect them to be run through the slot (though I expected the
NPG, too :)). And there does seem to be continuity between the BG
pins on the CPU backplane and those on the DD11.
If I remove the grant continuity card from slot 9, I can still boot
XXDP. If I remove a grant continuity card from the DD11 (with NPG
still intact), I can't -- it hangs as I'd expect with a hole in the
grant chain.
No one's done anything cute like hard-wiring the grants in and there's
no evidence of any modifications. All expected voltages are present
on the backplane pins in the right places. I put a little contact
cleaner in the slot too, just in case. I still can't get an SLU to
function in that slot, though the CSR addresses seem to respond and
the console/diagnostic PROM chugs along happily when I power the
machine up (though nothing appears on the serial line).
Tonight I may try running the SLU on an extender board and verifying
that all the proper voltages are actually making it to the board. The
fact that the board appears to be responding but I'm getting nothing
over the serial line makes me think that maybe the -15V isn't present
for some reason...
Annnnd: mystery solved (?). I had borrowed the SLU I was using in the
11/40 from my 11/34. This was an M7856 (DL11-W). Thought I'd grab
another SLU from my UNIBUS drawer and configure it up so I could put the
7856 back in the 11/34, but all I had left were the older, more annoying
to configure M7800s (DL11-D). So I jumpered it up (max of 2400 baud
with the crystal that's currently installed, blah) and installed it.
Works fine in the DD11 backplane.
Moved it to slot 9 of the CPU backplane. Still works.
So... maybe I just completely missed the memo on this, and maybe there's
still something wrong with my backplane... is it possible that slot 9 of
the 11/40's CPU backplane is wired *specifically* for an M7800? I guess
I need to spend some time tonight seeing what the differences are... but
now I need to go attend to a cranky 2yo who just woke up from a nap...
- Josh
