RE: Problems with 11/34A - VMS

This is a discussion on RE: Problems with 11/34A - VMS ; > -----Original Message----- > From: owner-info-pdp11@village.org > [mailto wner-info-pdp11@village.org] On Behalf Of John Wilson > Sent: Wednesday, April 27, 2005 11:36 PM > To: Info-PDP11@village.org > Subject: Re: Problems with 11/34A > > From: "Julian Wolfe" > > >I was ...

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Thread: RE: Problems with 11/34A

  1. RE: Problems with 11/34A

    > -----Original Message-----
    > From: owner-info-pdp11@village.org
    > [mailtowner-info-pdp11@village.org] On Behalf Of John Wilson
    > Sent: Wednesday, April 27, 2005 11:36 PM
    > To: Info-PDP11@village.org
    > Subject: Re: Problems with 11/34A
    >
    > From: "Julian Wolfe"
    >
    > >I was discussing this with Henk, and I think I've narrowed down the
    > >problem to the terminator - for some reason, instead of an

    > M9302 at the
    > >end of the UNIBUS, someone put a M930 there. If anyone here has a
    > >spare M9302 they don't want, let me know, cause I need one.

    > I know the
    > >bus grants are there, there's one in each D slot below each

    > H222 card.
    >
    > My understanding is that the M9302 was a bug-fix replacement
    > for the M930, and the M930 was the original "official" Unibus
    > terminator. Could be wrong about that, but anyway I'd expect
    > the M930 to terminate the bus OK as long as there are no
    > unclaimed grants (which certainly shouldn't be happening just
    > from peeking and poking a non-running machine through the
    > front panel).
    >
    > Anything's possible (yes it could be the M930's fault), but
    > I'd say take a closer look at the grant chain. When I got my
    > first 11/34a home it had the exact same symptom, BUS ERR any
    > time you try to do anything through the console. It turned
    > out to be a missing board (which I'd paid for but they sold
    > to someone else, thanks a lot), so I etched a G727 clone and
    > got it running.
    >
    > OK, you already said you have G727s in every slot, but it
    > might be worth doing a more systematic search -- for
    > starters, isolate the CPU backplane, i.e.
    > unplug the M920 or M9202 that connects it to the next
    > backplane over, and put the M930 (or M9302 if you can get
    > one) in its place (in the CPU backplane, not the other one).
    > I'm assuming the memory is in the CPU backplane.
    >
    > If you still get BUS ERRs when you exam or depos, well never
    > mind (I'm wrong, put it back the way it was), but if not then
    > you've narrowed things down and you can go one backplane at a
    > time until you find it. Then within a backplane you can
    > remove all peripheral cards and replace them with G727s (or
    > if a DMA device, either a G7273 or a G727 plus temporarily
    > add the NPG jumper). That might help you find if there's a
    > device that's not passing grants properly.
    >
    > BTW have you noticed the priority jumper plugs that DEC used?
    > Each Unibus device which can cause interrupts will have a
    > tiny PCB somewhere on it (normally down near the edge
    > fingers), mounted as a daughterboard in a DIP socket. It's
    > kludgy but there's almost never any reason to change the
    > interrupt priority from the default so DEC didn't bother
    > making it easy. Anyway this plug will pass all but one of
    > the bus grant lines straight through, and the remaining one
    > is connected to the peripheral's interrupt circuitry. Well
    > of course my point is, if this priority plug is missing then
    > there's your broken grant chain right there. So if any
    > device has an empty DIP socket in it, be suspicious.
    >
    > I don't suppose you have a logic probe? They're crude but
    > really wonderful for sorting out this kind of thing. It just
    > takes a little patience...

    I have not a logic probe. Is it something worth purchasing?

    Also, be aware this is a single-backplane machine, it has 9 slots on a
    DD11-PK, and that's it.

    This is my machine configuration: (where Nx is slots used
    A B C D E F
    1. M8266---------------------------------
    2. M8265---------------------------------
    3. M9301--------- M7859------------------
    4. M7850--------- M7800------------------
    5. H222----------------------------------
    6. G727-
    7. H222----------------------------------
    8. G727-
    9. M930----

    I'm going to doublecheck those grant cards to make sure they're all the way
    in tonight when I get home.

    Thanks!

    > John Wilson
    > D Bit
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  2. Re: Problems with 11/34A

    Julian Wolfe wrote:
    > I'm going to doublecheck those grant cards to make sure they're all the way
    > in tonight when I get home.


    Also make sure they are the right way around!
    It isn't the way you might guess..

  3. Re: Problems with 11/34A

    Julian Wolfe wrote:
    > This is my machine configuration: (where Nx is slots used
    > A B C D E F
    > 1. M8266---------------------------------
    > 2. M8265---------------------------------
    > 3. M9301--------- M7859------------------
    > 4. M7850--------- M7800------------------
    > 5. H222----------------------------------
    > 6. G727-
    > 7. H222----------------------------------
    > 8. G727-
    > 9. M930----


    You need a grant card in slot 9, too!

    Christian

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