11/70 board set on e-bay. . .

[Dave McGuire]

On Jan 14, 2008, at 10:02 PM, Richard wrote:
>> The 11/70 CPU is *not* a unibus backplane.  It is a *very* large
>> backplane that fills an entire BA11F.
>
> Interesting, I just assumed it was unibus.  Is the /70 the only PDP-11
> that has a custom backplane?  I thought the PDP-11 family had standard
> backplanes: unibus and Q-bus.

   No, (most) PDP-11s have standard *peripheral buses*, Unibus and Q- 
bus.  In fact, most (all?) Unibus PDP-11s have backplanes that are  
specific to the processor being used, as nearly all of them are multi- 
board sets (LOTS of boards in the case of the 11/70) and the card- 
edge connectors carry processor-internal signals, not high-level  
Unibus signals.

   Some PDP-11s have their memory on the Unibus or Qbus, and some  
don't.  The 11/70 (which I mention because that's what started this  
thread) does not.

   Some of them are "close relatives" like the 11/04 and 11/34, which  
share the same backplane.  In those systems, for example, the first  
few slots are not Unibus, but carry CPU-internal signals.  Later  
slots are Unibus.

   Qbus PDP-1s are more standardized across the product line.  Most  
(all?) of them use an all-Qbus backplane and the CPU is contained on  
one board.

            -Dave

-- 
Dave McGuire
Port Charlotte, FL