SIMH on low overhead platform

Paul Koning paulkoning at
Mon Aug 17 12:34:10 CDT 2020

> On Aug 17, 2020, at 3:43 AM, Tom Hunter via cctalk <cctalk at> wrote:
> Has SIMH been ported to a low overhead (instant-on) platform?
> I ask the question because the startup time of Linux is distracting when
> powering on a PiDP-11/70 or similar clone systems based on SIMH.
> Thanks
> Tom Hunter

I work with some storage systems (SAN arrays) that are layered on Linux and start in a small number of seconds.  I haven't actually timed how fast, but it's pretty quick.

NetBSD can also be made to start quite fast.

So I would think you could take your favorite Unix-style OS and trim out all the unnecessary cruft from the startup.  As an experiment, how fast does it start in single-user mode?  You should certainly be able to go that quickly.

Other options includes various RTOS.  There are some supported on BeagleBone, that might be an option.

I have wondered about running a minimal SIMH on Arduino.  The newer ones use ARM-32 cores of one kind or another.  I/O would be more limited, but it would be an interesting experiment to see if a small RT11 type system could run on a Trinket M0.  The specs suggest it might be doable: 256 kB flash, 32 kB RAM, 5 GPIO including UART capability.  Not a lot but certainly more than the small PDP-11 systems I ran RT11 V2 on.


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