>.. single PDP11 simulator can simulate different PDP11 models .


  Yes, and the UNIBUS and QBUS peripherals don't always map exactly in
functionality.  Actually I'm surprised this situation hasn't come up before
with other devices.


>Feel free not to use the extra ports that are provided free of charge.  J


  You're right - for the most part it doesn't matter.   But, . if you're
using the DZV/DZQ simulation with a TELNET port (which I imagine is what
most people do) then I don't think you can stop simh from accepting a
connection for lines 4..7 if the first four lines are already busy.  And if
you want to simulate a QBUS machine with 8 lines and two DVZ/DZQ cards, then
what the OS actually sees is all eight connections coming in on the first
card and none on the second card.  I haven't tried it yet, but I don't know
what the various -11 OSes will do when they get activity on lines that can't
physically exist.  Probably they use the same driver for both the DZ and DZV
so they won't care, but I don't know that.


>  What should happen when an odd number of DZV11's are configured and the
CPU type is changed .


Well, ideally there should be an error or warning message, but I imagine
that's difficult to implement.


  For me, I'd be happy if simh was changed to accept "SET LINES=." in
multiples of 4 rather than multiples of 8.  It's true that this would
possibly allow you to create invalid DZ configurations, but in my mind the
possibility of deliberately defining an invalid configuration is less
annoying than the impossibility of defining a valid configuration.



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