16 Nov
2007
16 Nov
'07
12:24 a.m.
Ethan Dicks wrote:
Good to know, thanks for helping me dip my toe into the Unibus pool.
Obviously, I haven't done my homework when it comes to Unibus. That's
this weekend's project. I'm going to move fairly slowly, and carefully,
with this system since I'm so far behind the curve at this point.
Okay, good confirmation from the two of you eases my mind, and this is
exactly what I plan to do until I get some mass storage interfaces. I'm
still 'in the market' for some of those system diagnostics, if anyone
can dig any up.
No, the
"middle" slots of the backplane are different than the first and
last (UNIBUS IN/OUT) slots.
Pat, you beat me to it, but let me add that in some cases, where you
have MUD (Modified Unibus Device) slots, it can be *very bad* to stick
a terminator in a peripheral slot. I'm pulling out of the back of my
memory that it's really, really bad to do that to an 11/725 or 11/730 -
you can blow the power supply.
The important thing to remember is what Pat already
said - the in/out
slots are different from the ones in the middle.
Unlike OMNIBUS or VME or ISA busses, the Unibus is not a simple
pin-1-to-pin-1, pin-2-to-pin-2 kind of pattern.
Yes, that's coming through loud and clear, and I appreciate it.
What you can
do, however, is pull the M9202, and put the terminator in
its place (in the CPU backplane side, not the UNIBUS backplane side),
and just ignore the UNIBUS backplane entirely. That's probably the
best thing to do for now.
That should work quite satisfactorily until you have a Unibus controller
you'd like to boot from.
G727s were very common in the day. What was less
common were the dual-
height GC7273 (or Software Results' GC747) grant cards that also jumpered
the NPR wire. If you are down to the booting stage and you get strange
behavior, be sure to check your NPR wires. Disk and tape controllers
tend to need the NPR wire off the backplane to be able to make the
"Non Processor Request" (to initiate what is called in other architectures
a DMA cycle), some comms controllers like the DMF32 also need the NPR
wire off, while other comms controllers like the DZ-11 don't need it,
so it should be jumpered on the backplane, if the card doesn't happen
to jumper it at the card edge (newer peripherals might, older peripherals
won't).
Also good to know. I' have noticed what I think are the NPR wires on
the backplane pins, and after looking again, I can readily see that the
two end slots are definitely wired up differently than the others. I
see, too, where signals are/were pulled off for the original DZ11 and
other devices that must have been in the backplane at one time. As I
said, I'm going to go slow on this, since prior experience and
self-education is still lacking. We'll take baby steps at first here.
I hope you guys don't mind answering such newbie questions, there will
definitely be more to come! ;-)
The "easy" way is to remove all the NPR
wires from all nine slots
in a DD11-DK, then use dual-height grant cards. The harder, but
less expensive way is, to check the needs of your cards and adjust
the backplane accordingly. If you don't make frequent changes, it's
not as bad as it sounds. If you are changing cards every month (as
we did, for development, etc), nine dual-height grant cards is cheaper
than an hour or two of head-scratching.
Well, I'm sure that once I get a UDA50 and/or some flavor of SMD
controller I won't be fiddling with the configuration much more. So, if
I can cross the Unibus configuration bridge safely once, I'll probably
be okay going forward.
We had an 11/750 that couldn't talk to its tape
drive out of the box.
Turns out we had forgotten to remove the NPR wire for that slot. I
think it was 4 hours before we remembered to check (since all of our
other machines had *no* NPR wires, we got out of the habit of looking).
Ha! Hopefully I remember to review this thread when the time comes for
my disk controller installation(s)! :)
- Jared