Announcing the Open SIMH project

Paul Koning paulkoning at
Fri Jun 3 14:52:24 CDT 2022

Announcing the Open SIMH project

SIMH is a framework and family of computer simulators, initiated by Bob Supnik and continued with contributions (large and small) from many others, with the primary goal of enabling the preservation of knowledge contained in, and providing the ability to execute/experience, old/historic software via simulation of the hardware on which it ran. This goal has been successfully achieved and has for these years created a diverse community of users and developers. 

This has mapped to some core operational principles:

First, preserve the ability to run old/historically significant software. This means functionally accurate, sometimes bug-compatible, but not cycle-accurate, simulation.

Second, make it reasonably easy to add new simulators for other hardware while leveraging common functions between the simulators.

Third, exploit the software nature of simulation and make SIMH convenient for debugging a simulated system, by adding non-historical features to the environment.

Fourth, make it convenient for users to explore old system environments, with as close to historical interfaces, by mapping them to new features that modern host operating systems provide.

Fifth, be inclusive of people and new technology. It's serious work, but it should be fun.

Previously, we unfortunately never spent the time to codify how we would deliver on these concepts. Rather, we have relied on an informal use of traditional free and open-source principles.

Recently a situation has arisen that compromises some of these principles and thus the entire status of the project, creating consternation among many users and contributors.

For this reason, a number of us have stepped up to create a new organizational structure, which we call "The Open SIMH Project", to be the keeper and provide formal governance for the SIMH ecosystem going forward.  While details of the structure and how it operates are likely to be refined over time, what will not change is our commitment to maintaining SIMH as a free and open-source project, licensed under an MIT-style license as shown on the "simh" repository page.

It is our desire that all of the past users and contributors will come to recognize that the new organizational structure is in the best interests of the community at large and that they will join us in it. However, this iproject as defined, is where we intend to contribute our expertise and time going forward.  At this point, we have in place the following, although we foresee other resources being added in the future as we identify the need and execute against them:

A Github "organization" for the project at

A Git repository for the simulators themselves at

The license for the SIMH simulator code base, found in LICENSE.txt in the top level of the "simh" repository.  

The "SIMH related tools" in This is also licensed under MIT style or BSD style open source licenses (which are comparable apart from some minor wording differences).

A "SIMH Steering Group" -- project maintainers and guides.

The conventional git style process is used for code contributions, via pull request to the project repository. The Steering Group members have approval authority; this list is likely to change and grow over time.

By formalizing the underlying structure, our operational principles and guidance can best benefit the community. These are being developed and formalized, with a plan to publish them soon.

We have used our best judgment in setting up this structure but are open to discussion and consideration of other ideas, and to making improvements. Many of us have been part of different projects and understand that past mistakes are real. We have tried to learn from these experiences and apply the collected wisdom appropriately. We desire to hear from the community as we update and refine the operating structure for the Open SIMH project.

We hope for your patience and look forward to your support as we work to refine the organization and be able to provide this wonderful resource for anyone to use as we continue to evolve the technology provided by the SIMH system.

    The SIMH Steering Group
       Clem Cole
       Richard Cornwell
       Paul Koning
       Timothe Litt
       Seth Morabito
       Bob Supnik

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