[Simh] Unibus XOR Tester

[Tim Shoppa]

Walter writes:
> when looking through a few listings of XXDP tests, I saw code
> sections mentioning a

>	XOR Tester

> This was obviously a Unibus device at address 177060.

A internal DEC memo mentions "PDP-11 Enginerring (Larry Condon)
has developed an XOR tester for small peripheral controllers that
plug into DD11 backpanels."

  http://www.bitsavers.org/pdf/dec/pdp11/memos/731015_Controllers_Cables_Packaging.pdf

This was the realization I think that a SPC could fit into a single slot instead
of requiring its own little backplane per device.

I always enjoyed running XXDP to abuse peripherals but I never had
much faith in it to provide me with useful information to
debug Unibus configurations.

Certainly Field Circus would show up with a test module and try to
run diagnostics on a machine that was shooting flames out of its
power supply :-).

Tim.