VAX 11/750 Config and Diagnostics, anyone?
ethan.dicks at usap.gov
Thu Nov 15 02:55:37 CST 2007
On Thu, Nov 15, 2007 at 03:11:36AM -0500, Patrick Finnegan wrote:
> On Thursday 15 November 2007 02:48, J Blaser wrote:
> > > You will need to have G727 or G7273 grant continuity cards in all
> > > of the empty slots....
> > Ah, I don't have any of those. Being a unibus noob, let me ask if I
> > can just move the M9313 terminator up, right 'behind' the DZ11,
> > and skip the empty slots? Or is there some 'special' wiring on the
> > unibus backplane. Admittedly, I've only worked with simple qbus
> > stuff to date, and a backplane with wirewraps all over it has me a
> > little nervous, to say the least. :)
> 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.
There were, back in the day, configuration guides for various system
setups. Unfortuately, all Unibuses are not created equal, especially
those in CPU cabinets. There is a great deal of overlap in that a
TU80 controller or a DZ-11 or a UDA50 will work in pretty much every
instance I can think of, but exceptions do lurk around the edges.
One egregious example I can think of is the COMBOARD-I. It works
in a DD11-DK (like the Unibus backplane in your 11/750), but *not*
in the Unibus slots of the CPU backplane of an 11/730. The fault
is with the original layout of the COMBOARD-I, not the 11/730, but
it was caused by an incomplete understanding of where the Unibus
signals were supposed to live in an SPC (Small Peripheral Controller)
slot. I have a "modified COMBOARD-I" with lots of blue wires
relocating the signals to the proper edge fingers. Fortunately, the
lesson was learned before the COMBOARD-II, which works in all types
of Unibus slots.
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.
> 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.
> You'll want to get grant cards eventually, they're fairly common and not
> too expensive. I've recently acquired a couple hundred (!) G727's.
> Send me a message off-list if you want me to send you a 10 pack. :)
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
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.
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).
Ethan Dicks, A-333-S Current South Pole Weather at 15-Nov-2007 at 08:30 Z
South Pole Station
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Ethan.Dicks at usap.gov http://penguincentral.com/penguincentral.html
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