> BA23 number 2:
> Front bays: an RX50
> Backplane:
> 	A	B	C	D
> 1	empty
> 2	M9405
> 3	empty

Yes, someone has pulled something.  Q-bus continuity is broken here.

> Now to me, that doesn't look right.  The BA23 is QQ/CD for the top 4
> slots and QQ/QQ serpentine for the bottom 4 - right?

Close; I think it's 3 QQ/CD and 5 QQ/QQ - the markings on the case
indicate, IIRC.  But the empty slot 3 will definitely break Q-bus grant
continuity.  (But make sure it's really empty; I've seen grant
continuity cards that were only about three inches high, and while they
were for UNIbus, not Qbus, such a thing may exist for Qbus.)

I don't recall what the M9405 is, but to make a usable machine you need
at least one CPU and one card of memory (there's only 1M on the CPU),
so there's clearly something missing.

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