qbus module ID

[Eric Smith]

Megan wrote:
> As far as I know, ALL of the KDJ11-B boards are qbus, period.  Some of
> them may only be usable specifically in the 11/84, but remember that the
> first part of the 11/84 bus is qbus and there is a q-to-u converter.

Note that when a KDJ11-B (M8190) is installed in an 11/84, it's not really
talking Qbus.  It's talking a modified Qbus/PMI bus protocol, which
will only work with the KTJ11-B (M8191) Unibus adapter.  Same applies
to the KDJ11-E (M8981).

For the same reason, the KTJ11-B can't be used as a Unibus adapter
for any other Qbus masters, since it doesn't talk normal Qbus.  It
only works with the KDJ11-B (M8190) and KDJ11-E (M8981) CPUs.

The KDJ11-B and KDJ11-E distinguish whether they're installed in a Qbus
or Unibus system by the PMI PUBSYS signal.  The KTJ11-B adapter asserts
this signal.  WHen these CPUs are used in a Qbus system, the signal is not
asserted, so the CPU module uses normal Qbus and PMI protocols.

This documented to some extent in chapter 3 of the Preliminary PDP-11/84
System Installation and Technical Reference Manual (EK-1184A-TM-PR2),
and chapter 5 of the PDP-11/94-E System User and Maintenance Guide
(EK-PDP94-MB-001), both of which can be found on bitsavers.org.

Eric