qbus module ID

From: Eric Smith <eric_at_brouhaha.com>
Date: Fri Feb 11 14:44:56 2005

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.

Received on Fri Feb 11 2005 - 14:44:56 GMT

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