[Simh] Pdp8 terminals

[Mike Barnes]

I haven't look at this code in a long while, but from what I can recall,
the issue is with the 'pdp8' implementation. There are two pieces at play:
one is the generic multiplexer used by all the simh simulators, and the
other is the particular interface which emulates the pdp8 terminal driver.

The generic simh multiplexer can handle lots of ports... for example, on
the PDP10 simulator, the default is 32 lines.

In the pdp-8 simh code, I seem to remember that part of the code used
arrays for the ports (so it could be expandable), and then in some places
it was just hard coded. It's not due to any limitation with actual DEC
hardware. It's just how it's implemented. I'm not sure how easy or hard it
would be to expand.

Again, this is from old knowledge, so I may be off here.

Mike

On Mon, Sep 5, 2016 at 1:11 PM, Gene Irwin <girwin1215 at gmail.com> wrote:

> I have been looking at the ttix/ttox interface.  Simh seems to only
> support one unit of 4 ports.
>
> But tss8 supports 8 users. So does edusystem 20 and 25.
>
> Is this only a simh limitation, a user error, or some strange hardware
> configuration I amassing?
>
> ttox shows 4 units. I don't see a way to modify this.
>
> In high school I used a pdp-8/e with edusystem 25 and 8 users. But 5 were
> Dec writers and 3 were teletypes on dialup.
>
> So the other 3 used a different interface maybe?
>
> I can't find any hardware requirements for edusystem configurations other
> than core and storage.
>
> Anyone have any ideas?
>
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