[Simh] SDS Card Reader

[Mark Pizzolato]

Hi Ken,

On Wednesday, February 12, 2020 at 10:51 AM, Kenr wrote:
> I'm interested in using the SDS 940 simulator to run programs from the XDS
> PAL tapes found on bitsavers.
> Most of these programs were loaded onto the PAL library tapes from punched
> cards by SDS/XDS in a self loading format for distribution to
> customers.  Customers would copy the files from tape onto punched
> cards.  The self loading programs assume a card reader, not a paper tape or
> mag tape.
> 
> The SDS 940 simulator does not have a card reader driver so  I have a couple of
> questions.
> 
> 1. Why isn't there a card driver for the 940?
> 2. I notice simulators for similar machines also don't have card drivers,  why is
> that?
> 3. Does anyone know of a (maybe unfinished, unofficial) card driver that I
> might use?
> 4.  Where might one find the developer documentation mentioned in the simh
> faq?
> 
> Anyone care to answer these or offer an opinion on driver development?

From a simh point of view, the terminology for what you're looking for is a 
card reader/punch device simulator.  I can't personally speak to why such a 
device simulator hasn't been implemented for any particular simulator, but
the likely reasons may be: 

1) Lack of precise documentation for the programming interface to the 
     hardware in question.  Sometimes this is available in specific hardware 
     documentation or even schematics, other times the programming 
     interface can be specifically extracted from the pieces of software 
     (aka OS drivers) that manipulated a particular device.  This is most easily
     observed if this software is available in source rather than binary form.
2) Lack of interest for a particular device by the folks who developed or 
     added to the existing system simulator.

It seems like your interest is now addressing point #2, so given your 
interest if you can find sufficient documentation to address the how 
the software should interact with this device, you'd be welcome to
come back here and ask for help implementing it.  Myself or others 
will certainly be able to stand up and provide some nuts and bolts 
guidance.  Simh has a 'library' that is designed to specifically interface 
with and create virtual card decks on modern systems, so the missing 
pieces are really how the hardware looked to the software that uses 
it.  This library was created by Rich Cornwell and is call sim_card.c.
Bob Supnik wrote the SDS simulator and he and Mark Emmer have 
made somewhat recent changes.


Good Luck,

- Mark