MicroVAX II - TK50 problem

[Pete Turnbull]

On Mar 10 2005, 20:10, Adrian Graham wrote:

> the uVAX II has a Q22/Q22 backplane so the positioning of the TQK50
is
> important, as is the RQDX(2/3) disk controller which should be last
on the
> bus.

No.  It's only the RQDX1 that has the "must be last on the bus"
problem, and only then if what's below it uses DMA  and interrupts.
 RQDX2 and RQDX3 have no such limitation.  You won't find an RQDX1 in a
MicroVAX II because it is not compatible with the MicroVAX II
processor.

> The first 3 slots are CD types and are reserved for CPU/Memory, the
> rest (I can't remember which size cab you've got) are serpentine so
if
> you've only got the CPU, 2 mem boards and the disk/tape controllers
then the
> TQK50 should be on top of the RQDX3.

Well, as you mention the cabinet size, perhaps you realise this, but
I'll spell it out:

The backplane in a BA23 is three Q22-CD slots followed by serpentine
slots; the BA123 is 4 slots of Q22-CD then serpentine.  MicroVAX IIs
came in both types.  In either case, you must, of course, put the CPU
and memory at the top, but there is nothing to prevent use of any
remaining Q22-CD slot for anything else.  Just remember only the
left-hand side of a Q22-CD slot actually has Qbus signals on it (there
are some quad boards that won't work in a Q22-Q22 slot; I can't think
of any offhand that won't work in a Q22-CD slot but that doesn't mean
there aren't any).  The MicroVAX II Micronotes actually show such a
configuration, with a processor, single memory card, a DEQNA, an RQDX2,
and a DHV11 (with the DHV11 last, as usual).


-- 
Pete						Peter Turnbull
						Network Manager
						University of York