Computer Simulation and History

This site documents SimH, a simulator for historic computer systems, as well as papers and reflections on the history of computing.

SimH (History Simulator) is a collection of simulators for historically significant or just plain interesting computer hardware and software from the past. The goal of the project is to create highly portable system simulators and to publish them as open-source software on the Internet, with freely available copies of significant or representative software.

This site contains the "classic" version of SimH, the 3.X stream. It includes all of the simulators I wrote or maintain, as well as the current releases of J. David Bryan's HP simulators. It also has a collection of papers and software kits that are applicable to all versions of SimH.

The V4 stream is substantially enhanced and contains many additional simulators. It can be found on GitHub under the name Open-SimH.

The source code in both V3 and (Open SimH) V4 is licensed under an "MIT-style" open-source license. Contributions to either stream are welcome if (and only if) they include this style of open-source license.


SIMH is a highly portable, multi-system simulator.

SIMH V3.x implements simulators for:

Also available is a collection of tools for manipulating simulator file formats and for cross-assembling code for the PDP-1, PDP-7, PDP-8, and PDP-11.

Release Notes for V3.12-3

This release is mostly bug fixes, particularly in the PDP-11 and Sigma simulators. Support for running SimH on MacOS "Classic" (pre-OSX) and OS/2 has been dropped. See the detailed revision histories in individual source code modules for details.

Software Kits to run on SIMH

Help with SIMH

System Photographs

Papers on Simulation and Historic Hardware

DEC's Microprocessors (through 1992)

Updated 28-May-2023 by Bob Supnik (simh AT groups DOT io - anti-spam encoded)