MicroVAX II - TK50 problem

Ethan Dicks ethan.dicks at gmail.com
Thu Mar 10 17:41:58 CST 2005


On Thu, 10 Mar 2005 21:44:15 -0000, Adrian Graham
<witchy at binarydinosaurs.co.uk> wrote:
> > Qbus. However, I think you may have hit on something. The
> > RQDX3 is not at the end of the bus. If memory serves (I'll
> > verify this after I get home from work today), the backplane
> > arrangement is something like this:
> 
> Do you have grant continuity cards underneath the half-height cards? Ah, no
> - M9047 is a grant card....
> 
> I'd swap it to
> 
>       A        B        C        D
>  +-------------------------------------+
>  |                CPU                  |
>  +-------------------------------------+
>  |                Memory               |
>  +-------------------------------------+
>  |                DHV11                |
>  +-------------------------------------+
>  |                ???? **              |
>  +-------------------------------------+
>  |     TQK50*       |      RQDX3       |
>  +-------------------------------------+

There are *3* CD slots in a BA23.  Since I saw your reply that "this
works", let me give you one thing to look for... make sure that there
are no grant jumpers on the CD side of the DHV11 if you want to retain
this arrangement.  It's legal to tap power/ground when not using the
CD socket for what it's for, but it's important not to short any CD
data lines together.

You would *need* those grant jumpers in place when putting the DHV11
in any lower slot (a Q22/Q22 slot), but you want them out in slot 3
(Q22/CD).

Alternately, you could arrange the bus this way (and I _would_)

A--B--C--D
[ -- CPU --]
[ -- MEM --]
[TQK50][empty]
[-- DHV11 --]
[-- mystery card --]
[RQDX3][empty]

The grant chain goes down through the TQ50, across the DHV11, across
the mystery DMA card, then down to the RQDX3.

You could also put the M9047 grant card in the AB side of slot 6 and
the RQDX3 in the CD side of slot 6, in case you wanted to leave room
for a dual-height option later.

-ethan



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