<I don't have a MicroVAX CPU board in my hands this morning to verify
<some of this.  My understanding of the CD interconnect is that on the
<backplane there are connections between several contacts on the "2"
<side of one card and corresponding contacts on the "1" side of the next
<card.  To show my rack-mount BA-23 orientiation, I think of these as
<the bottom side of one card connecting to the top side of the card
<below it.

Not for the h9278 and friends.  The situation is the BA23 CD is and ba11 
versions of CD interconnect are not identical.

<which is the logical equivalent of the BA-23 top, you could have
<CPU, Memory, CPU, Memory.  And two short PMI cables, one for each pair
<of boards.

No can do as the CD is bussed all the way down the four slots.  I beleve
you could have cpu, AB bus grant, AB bus grant and memory and it's treated 
the same as if they were adjacent.

<There may be some things buried in the fine print of the CD
<interconnect, about connections that are bussed through, besides the
<standard power and ground.  I am trying to remember which DEC small
<handbook has the wiring diagram of the CD interconnect.  It must be one
<of the two blue ones that came out around 1985-6.

The backplane for the ba11(in the blue books) is not the same as the
H9278 (ba23) or the one used in the ba123.  The CD sides are wired 
according to microvax memory interconnect and for the h9278 slots 1,2,3
of the CD bus are one bus.  This also applies to slots 1,2,3,4 of the 
ba123.

<A side thought -- the first generation of CD-interconnect backplanes
<had 9 QQ-CD slots.  Of course they had only 18-bit address wiring, but
<that's pretty easy to fix.

Also not all the first generation backplanes were terminated the same and
a few not at all.  The VAX would not like that.

It a feature that makes putting two ka630s in one box and having PMI 
memory for both.  I believe the slave mode also cuts off the bus drive 
to the CD connectors so it will not conflict with the master.  that 
limits the slave ka630 to local memory only (1mb).  Still with an 
assembler and tight C coding the 1mb is plenty for a lot of specific 
tasks.

Allison