Last updated
Developer(s) Robert M. Supnik
Initial release1993 [1]
Stable release
3.10 / February 24, 2019;9 months ago (2019-02-24)
Preview release
Repository OOjs UI icon edit-ltr-progressive.svg
Written in C
Operating system Windows, Linux, macOS, FreeBSD, OpenBSD, NetBSD, OpenVMS
Platform x86, IA-64, PowerPC, SPARC, ARM
Type Hardware virtualization
License MIT (modified)

SIMH is a highly portable, multi-system emulator which runs on Windows, Linux, macOS, FreeBSD, OpenBSD, NetBSD and OpenVMS. It is maintained by Bob Supnik, a former DEC engineer and DEC vice president, and has been in development in one form or another since the 1960s.



SIMH was based on a much older systems emulator called MIMIC, which was written in the late 1960s at Applied Data Research. [1] SIMH was started in 1993 with the purpose of preserving minicomputer hardware and software which was fading into obscurity. [1]

Emulated hardware

Version 6 Unix for the PDP-11, running in SIMH Version 6 Unix SIMH PDP11 Emulation KEN.png
Version 6 Unix for the PDP-11, running in SIMH
Version 7 Unix for the PDP-11, running in SIMH Version 7 Unix SIMH PDP11 Emulation DMR.png
Version 7 Unix for the PDP-11, running in SIMH
"4.3 BSD UNIX" from the University of Wisconsin, on a simulated VAX. 4.3 BSD UWisc VAX Emulation Login.png
"4.3 BSD UNIX" from the University of Wisconsin, on a simulated VAX.

SIMH emulates hardware from the following companies.

Advanced Computer Design




Control Data Corporation

Data General

Digital Equipment Corporation

GRI Corporation



Hobbyist projects




Lincoln Labs – MIT Research Lab

Manchester University



Sage Computer Technology

Scientific Data Systems


Xerox Data Systems

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  1. 1 2 3 "Preserving Computing's Past: Restoration and Simulation" Max Burnet and Bob Supnik, Digital Technical Journal, Volume 8, Number 3, 1996.