[Simh] SCSI-Interface for simh-vax?

[Mark Pizzolato]

On Saturday, September 1, 2018 at 10:45 AM, Eberhard Heuser wrote:
> Are there any plans to add a SCSI-Interface to the VAX-code?
> 
> I want to add the CD-R burning capability but there is no interface
> (SCSI or IDE) that allows to communicate on the diagnose level
> with an CD-drive.
> 
> I have seen that one can access a physical CD-drive but only through
> the pudriver and not via the pkdriver.

Well, none of the current VAX simulators had a native SCSI interface 
which was interfaced with the pkdriver.  Without a simulated system
there is no place for SCSI support.

Meanwhile, 99%+ of the host systems are natively capable of burning
CD/DVD.  I am not aware of any DEC supplied software running on 
VAX/VMS which was capable of producing a CD image in the ISO 9660 
file system format.  All CDs that I ever encountered on DEC systems 
(produced by DEC for use on VMS systems) had ODS2 file systems on 
the CD media.  All of the existing VAX simulators can easily produce an
ODS2 disk image of arbitrary size which can then be readily written on 
the host system to CD or DVD media with host supplied tools.

Even if a simulator comes along which does have a built in SCSI support,
arbitrarily extending that support to interface with CD/DVD media for 
burning activities would be a challenge to achieve in a portable way 
to work on most host platforms and as such probably won't get done
unless you're interested in taking on the project.

After thinking a little more, I vaguely recall that there was indeed a 
Qbus board which had a SCSI chip that used the PKDRIVER.  This
was called the KZQSA.  I tested one once and was fundamentally
unimpressed by its performance primarily due to it not being a
DMA device.  In any case, I haven't seen any detailed documentation
on this board which would be necessary to write a simulator of it, 
but if you can find documentation, feel free to take a crack at
simulating it, and delving into the host platform complexities (in 
a portable way) to burn CD media.

- Mark