[Simh] Making "Stripped Down" Simulator Builds + Other Queries

[Mark Pizzolato - Info Comm]

On Saturday, July 06, 2013 at 10:39 AM, Christian Gauger-Cosgrove wrote:
> I've a few questions regarding SIMH.
> 
> The first question I have is:
> Is it possible to create a build of a specific emulator that has been
> stripped or pared down to a specific configuration? E.g. instead of
> the full PDP-11 simulator, building just a PDP-11/23 (with FPP, no
> CIS), with 256KB of RAM, a pair of RL02's and a quartet of serial
> ports (as an example system); or as another example, a PDP-8 with EAE,
> 4K of core, and a single console teleprinter.

All of these are theoretically possible, however the benefit would 
hardly be very significant.  The largest current simulator is just 
about 1MB in size including all current device simulations.  The 
simulated RAM is dynamically allocated, so that wouldn't matter 
one way or another.  Essentially any target platform you'd hope 
to run on likely uses virtual memory and thus would only contain 
(in memory) more or less the code for the devices you are actually 
Using.

All the current simulators run fine on a $35 Raspberry Pi, so it 
would be hard to imagine shooting for a smaller target.  Even so,
the existing simulators depend on a basic set of runtime capabilities 
which are met well by any current Linux platform.

> The only other question I was wondering, is would it be possible to,
> subsume a simulator into another program/application? While some of
> you following this mailing list will probably find the idea silly, but
> an idea was put forth among my circle of friends of trying to get a
> subset of one of the SIMH simulators (we're still debating whether to
> use the VAX, PDP-11 or Z-80 S-100 bus system) as a flight computer for
> Kerbal Space Program. (You may commence laughing... now.)

You could probably do that or merely run a simulator (in a subprocess) 
from another program.

> A third question, somewhat applicable to the above, but is there a
> place where one can find some documentation/information on adding a
> device to one of the simulators? I and my friends find the need to
> create an interface akin to the DRV11-J (that's the card with the four
> 16-bit wide parallel interfaces with handshaking/flow control lines).

One could write a simulated device using info that Dave Bryan pointed 
you at.

Alternatively you could use a network capable simulator (VAX or PDP11) 
and communicate with the simulated system via the network.

An additional alternative for any simulator would be to use one of the 
existing multiplexor devices (terminal port emulation) can be connected 
inbound (via an arbitrary listen port) and/or outbound to a tcp 
listening port in another application.

- Mark Pizzolato