> On Apr 9, 2018, at 6:25 PM, Mark Pizzolato <m...@infocomm.com> wrote:
> 
> ...
> With simh as it is currently written, all of your DZ devices do need to 
> be configured to have adjacent CSR address blocks and Vectors.  
> They can't separately be scattered around the I/O space.

That conforms to the float rules, so it seems like a reasonable restriction.  
It's theoretically possible to configure real hardware differently, and in some 
OS you can then still talk to the devices (by setting addresses manually) but 
it would not be a standard config and probably not supported.

>> ...
>> I'd like to have more than 4 disks on one MSCP controller. There is 
>> absolutely
>> no reason for the limit of 4. That's just an implementation detail on some of
>> the existing MSCP controllers, but there are MSCP controllers who also take
>> more than 4 disks.
>> 
>> And that exists in real life, and I cannot do that (and a bunch of other
>> setups) in simh, so I'd say that simh is rather more limited than real life. 
>> :-)
>> 
>> Same story for TMSCP.
> 
> Please identify Qbus or Unibus controllers that had hardware support for 
> connection of more than 4 units and I'll include those controllers (with 
> their limits) in the simulator.  A pointer to the documentation for these
> devices would be helpful.

I don't remember controllers with more than 4 units per device, but MSCP unit 
numbers are arbitrary 8 bit values.  So a limit of 4 units is proper, but a 
limitation on those unit numbers being 0..3 is not accurate.  It matters in 
some OS.  For example, VMS has type/controller/unit addressing (DUA3 etc.) but 
RSTS does not.  So on RSTS, if you have more than one MSCP controller, they 
must have disjoint unit numbers.  Since the unit numbers are 8 bits, that's 
easy to do.  But I don't see how I can do that in SIMH.

        paul


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