This is indeed true.  The problem comes from the fact that the single PDP11 
simulator can simulate different PDP11 models some of which are Unibus while 
others are Qbus systems.  On the various VAX simulators, each simulator only 
simulates either a Unibus or a Qbus machine and thus things are simpler to 
align and thus things appear as you would expect.

Feel free not to use the extra ports that are provided free of charge.  :)

Seriously, I'll look into addressing this.  The number of DZ11/DZV11 devices 
that are simulated is derived from the number of lines which are configured.  A 
problem arises when the CPU type changes between a Unibus and Qbus types.  What 
should happen when an odd number of DZV11's are configured and the CPU type is 
changed from a Qbus type to a Unibus type?

From: Simh [] On Behalf Of Robert Armstrong
Sent: Monday, April 9, 2018 7:35 AM
Subject: [Simh] DZ11 vs DZV/DZQ11

  It appears that if you want to simulate a DZV or DZQ11 on a QBUS PDP11, then 
you have to use the UNIBUS DZ11 instead.  That's OK, except that a DZ11 has 8 
lines per card where as the DZV and DZQ are only 4 lines per card.  Simh won't 
let you say "SET DZ LINES=4".  This is something of an issue because I want to 
set up my simh environment to exactly mimic my real hardware, and it appears 
that's not possible as far as the DZ goes.

  Or am I missing something??

  BTW, it's funny that "HELP DZ" in simh talks exclusively about the DZV11 and 
even says things like

... The DZV11 is a 8 line terminal multiplexor. ...

That's totally wrong...

Bob Armstrong

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