Kearney & Trecker Core memory, may be PDP8

Jon Elson elson at
Wed Nov 12 11:27:59 CST 2014

On 11/12/2014 09:43 AM, Johnny Billquist wrote:
> There were definitely quad height boards, but I don't 
> think I ever saw a PDP-11 board that was hex height with 
> only four edge connectors. But I'm sure you will point me 
> to one now. :-)
There definitely existed such boards.  I don't remember if 
these were made by
DEC or 3rd party.  The idea was that the Unibus backplane 
segments had
9 hex-wide slots.  The two end slots had the Unibus in and 
out jumpers/cables
plugged into them.  if a board was hex wide at the handle 
end, but cut
down to quad wide for a couple inches at the connector end, 
it could
fit in those end slots, which were often left unused 
otherwise. Later
DEC went to the full-height Unibus jumpers with about 5 feet 
of cable in them
to clean up bus signals, and this scheme didn't work 
anymore.  But, it
did with the old short Unibus jumpers.

And, of course, the very OLDEST PDP-11 peripherals were 
built up out of a
bunch of dual-wide boards.  There were standard boards such 
as address
recognizers and 16-bit registers, And so a parallel or 
serial interface would
take up a whole Unibus backplane segment with half a dozen 
in it.


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