[Simh] The missing PDPs

[Warren Young]

On Mon, Aug 12, 2019 at 7:54 PM Ray Jewhurst <raywjewhurst at gmail.com> wrote:

>
> Has any ever thought of writing simulators for the two missing systems,
> the PDP-5 and the PDP-12?
>

Are you reacting to this recent post over on the PiDP-8/I list?

    https://groups.google.com/d/msg/pidp-8/1Rdv-Syg9H4/_KSeiGkmEgAJ

If so, that's probably a pretty good list of starting tasks to modify the
existing PDP-8 emulators to suit.

If not, then that's a funny posting coincidence!

That list can't be complete. For one thing, the existing PDP-8 simulator in
SIMH has a lot of support for features added to the Family of 8 after the
"straight 8" came out. SIMH's PDP-8 simulator is closest to a very
tricked-out PDP-8/e with several PDP-8/a features thrown in besides. You'd
have to rip a lot of that out to make it properly emulate a PDP-5 instead.

I think you'd want to do this by forking the existing simulator, not by
trying to ifdef your way towards a combined simulator that will do both.

As for the PDP-12 idea, that you could probably do as a special device for
the existing PDP-8 simulator. You do, after all, enter LINC mode via an IOT
instruction, and that's already handled by the existing PDP-8 simulator
code by SIMH device handlers. The only tricky bit is that once in LINC
mode, you go off and don't come back until the LINC code tells the
processor to return to PDP-8 mode. Basically, you'll end up ping-ponging
between two very different simulators.


> my knowledge of C is somewhere between beginner and intermediate
>

The best way to change that is to start a project that you care about
deeply enough to spend the time it takes to push past your current
limitations. Many an incompetent ends up one of the field's respected
gurus. It "just" takes work.

Any advice, suggestions or just plain criticism of this idea would be
> welcomed.
>

Find some bit of PDP-5 and/or PDP-12 software that you want to make run,
then modify the current simulator until it does run.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.trailing-edge.com/pipermail/simh/attachments/20190812/c8fad6b1/attachment.html>