UNIBUS extension card/cable sets Was: Looking fo

Paul Anderson useddec at gmail.com
Mon Jun 22 13:18:44 CDT 2015

The 3 bergs to unibus was used in the RK8-E, the unibus end plugging into
the first physical drive.

Between unibus backplanes were always M920, M9202, bus margin jumpers,
which i can't remember the part numbers, and various Albe and other non-dec
options. The cable was always a BC11A-XX, i think 2 to 25 or maybe 50 feet.
This is from the PDP11 world. i never played with the 725, 730, or 750.

On Mon, Jun 22, 2015 at 11:23 AM, John Wilson <wilson at dbit.com> wrote:

> On Mon, Jun 22, 2015 at 11:46:08AM -0400, Noel Chiappa wrote:
> >    > I've seen M9014s only at the far end of the UBAs on a KS10, so it
> >    > wasn't taking the place of a BC11.
> >
> >??? If it wasn't take the place of a BC11 (i.e. proving a path for the
> >out), what was it doing?
> OK then I guess it *was* taking the place of a BC11. :-)  I just meant it
> wasn't jumping directly from one DD11 to another, so the "source" end
> really was three Bergs, not a DD11 slot.  I've seen that done only with the
> fancy flexprint cable, not two paddles and three ribbon cables, so I was
> kind of assuming that there's some impedance-matching (etc.) problem with
> using ribbon cables for more than one hop.  But then again ...  I chose the
> digital version of EE as my major precisely because I knew I'd flunk Fields
> and Waves.  Transmission lines are black magic as far as I'm concerned!
> John Wilson
> D Bit

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