[Simh] SDS Card Reader

[Mark Emmer]

I'd be very surprised if any SDS 940s had card readers or punches. They are remnants from the days when we all marched down to the machine room and passed boxes of 2,000 cards through the window to the operator to run in a batch environment. In 1965, the Berkeley time sharing system on the 940 was meant to break that model -- users would create programs interactively via remote teletypes.  No cards needed or wanted.

That said, the SDS 940 Reference Manual describes the card reader and punch I/O instructions in detail and provides example code for operating both devices in both Hollarith and binary formats. The logic was retained from its non-time sharing predecessor, the SDS 930.

Quickly glancing at sim_card.c, it should be straight-forward to wire up a card reader and punch driver for the 940 simulator. sim_card supports binary mode, which would be used by Ken's boot program.  Unfortunately, I can't volunteer to do that now as I have too many other higher-priority projects on my plate.

I've been in contact with Ken privately about using the 940 simulator in "normal" (SDS 930) mode for his PAL tapes.  Seems quite feasible if he can get around the card reader issue.

Mark Emmer



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On Feb 12, 2020, 1:28 PM, at 1:28 PM, Mark Pizzolato <mark at infocomm.com> wrote:
>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 
>
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