[Simh] Issues with VH simulation and 4.3BSD-Quasijarus

[Paul Koning]

> On Mar 9, 2017, at 3:15 PM, dundas at caltech.edu wrote:
> 
>> So ...If the DHV is supposed to the simh emulation of the combination of a
>> DEC DH11 and DM11 pair (the DM11 was the modem control option for the DH),
>> then this should "just work"
> 
> The SIMH VH device is a simulation of the DEC DHQ device (M3107), a dual
> height Qbus board, normally supporting 8 lines and features DHU/DHV
> "compatibility."  DHV was an earlier quad height incarnation, while the
> DHU was a 16-line Unibus interface.  These are all similar to the historic
> DH/DM combination but not identical.

That sounds right.  DHV is a 8 line Qbus device inspired by DH, close but not exactly the same.  DHQ is essentially the same thing made physically smaller.  DHU is DHV ported to Unibus and 16 lines rather than 8.

Looking at some RSTS code...  DH11 is a different device table entry from VH (DHV/DHQ/DHU).  For one thing, it looks like VH has a different floating CSR rank.  In addition, the terminal driver has a port driver for DH11, and a separate port driver for VH.

So this suggests that if you want DH11 support, you'll want to add DH11 emulation (preferably with a DM11 option) to SIMH.

	paul