Darn, there was a mistake... so I had to redo it...
- - - - -
Let me answer like this...
In a BA123:
o The Qbus passes direct from slot1/ab to slot4/ab
o For slots 5-12, it does the serpentine (5/ab, 5/cd,
6/cd, 6/ab, 7/ab, 7/cd, etc...)
o All dual boards must be placed at some point in the
serpentine. For slots 1-4, this means AB. For
slots 5-12, this can be either AB or CD.
o Quad boards which may not go in CD must go in slots
5-12
o For quad boards which can be either CD or Q/CD, the
jumpers on-board must be set for the slot you are
placing it in (there should be a couple of jumpers
which are removed if the board is placed in a Q/CD
slot, 1-4, and installed if it is placed in a Q/Q
slot, 5-12)
o For quad boards which can only go in Q/Q, they may
only be placed in slots 5-12.
o If you follow the serpentine, there should be no
empty Qbus slots between the processor and the last
board in the bus (there are exceptions, but for now
regard it as a hard and fast rule).
o For any gaps in the serpentine, you should install
a M9047
o The RQDX1 is a mutant, since it doesn't pass any
grant signals, it must be the last board in the bus
o The RQDX2 tried to correct this, but didn't quite -
it must be the last DMA device in the backplane...
Non-DMA boards *can* be placed after it
That's it in a nutshell. For a BA23, the critical numbers are
slots 1-3 == Q/CD, 4-8 == Q/Q. There are also some backplanes
with Q/CD in all slots, and some which are Q/Q in all slots.
Know thy backplane!
Megan Gentry
Former RT-11 Developer
+--------------------------------+-------------------------------------+
| Megan Gentry, EMT/B, PP-ASEL | Internet (work): gentry!zk3.dec.com |
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Received on Mon Mar 08 1999 - 22:50:28 GMT