SIMH is a free and open source, multi-platform multi-system emulator. 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. History SIMH was based on a much older systems emulator called MIMIC, which was written in the late 1960s at Applied Data Research. SIMH was started in 1993 with the purpose of preserving minicomputer hardware and software that was fading into obscurity. In May 2022, the MIT License of SIMH version 4 on GitHub was unilaterally modified by a contributor to make it non-free, by adding a clause that revokes the right to use any subsequent revisions of the software containing their contributions if modifications that "influence the behaviour of the disk access activities" are made. As of 27 May 2022, Supnik no longer endorses version 4 on his official website for SIMH due to these changes, only recognizing the "classic" version 3.x releases. On 3 June 2022, the last revision of SIMH not subject to this clause (licensed under BSD licenses and the MIT License) was forked by the group Open SIMH, with a new governance model and steering group that includes Supnik and others. The Open SIMH group cited that a "situation" had arisen in the project that compromised its principles. Emulated hardware SIMH emulates hardware from the following companies. Advanced Computer Design PDQ-3 AT&T 3B2 BESM BESM-6 Burroughs B5500 Control Data Corporation CDC 1700 Data General Nova Eclipse Digital Equipment Corporation Alpha PDP-1 PDP-4 PDP-7 PDP-8 PDP-9 PDP-10 PDP-11 PDP-15 VAX Family Systems MicroVAX I, VAXStation I MicroVAX II, VAXStation II MicroVAX 3900 VAX 11/730 VAX 11/750 VAX 11/780 VAX 8600 GRI Corporation GRI-909 Hewlett-Packard 2116 2100 21MX 3000 Honeywell H316 H516 Hobbyist projects N8VEM IBM 650 701 704 1401 1620 1130 7010 7070 7080 7090/7094 System/3 Intel Intel systems 8010 and 8020 Interdata 16-bit series 32-bit series Lincoln Labs – MIT Research Lab TX-0 Manchester University Baby, or SSEM MITS Altair 8800 both Intel 8080 and Zilog Z80 versions Royal-Mcbee LGP-30 LGP-21 Sage Computer Technology Sage II Scientific Data Systems SDS 940 SWTPC SWTPC 6800 Xerox Data Systems Sigma References External links Additional VAX/MicroVAX models for SIMH Running VAX/VMS Under Linux Using SIMH Debian Package FreeBSD Port UNIX: Old School. Using SIMH to explore UNIX history - Matthew Hoskins Free emulation software Linux emulation software MacOS emulation software Windows