21 May
2007
21 May
'07
4:27 p.m.
On 21/05/2007 09:34, Johnny Billquist wrote:
Patrick Finnegan <pat at computer-refuge.org>
skrev:
Pat, what you have is what I would describe as an
11/93 with an
Qniverter. That will not be exactly the same thing as an 11/94.
The KTJ11-B, which is DECs Unibus adapter, have some special signals to
the CPU telling it that the KTJ11 is there, and that changes the
behaviour of the Qbus, according to the manuals.
Yes, by enabling the PMI, that's all.
I haven't said that the wiring of the memory slots
in an 11/84 (or
11/94) isn't the same as in a Q/CD backplane. It must (by default) be
atleast very similar to a Q/CD backplane.
It's exactly the same. Or to be precise, the A/B slots are normal
22-bit QBus; the relevant C/D signals are fully bussed on their top
surfaces, rather than just connecting the bottom of each slot to the top
of the next one down. That won't matter to PMI memory cards, which have
the fingers on the top surface connected to the fingers on the bottom.
Nor will it matter to a KDJ11-B, which (apart from power) has
connections only on the top surface.
However, there are some
special signals, and also some signals that change behaviour in an 11/84
and 11/94, according to the manuals.
The special signals are the standard PMI signals on C/D (plus one that
tells the processor it's in a Unibus system, IIRC), and the ones that
change are the ones that do so when moderated by the PMI protocol.
And that will only happen if you
have a KTJ11-B in there.
Or something else to assert the PMI :-)
--
Pete Peter Turnbull
Network Manager
University of York