12 Nov
2014
12 Nov
'14
5:27 p.m.
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
boards
in it.
Jon