SIMH

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 no longer free software, 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

Norsk Data

 * Nord-100

Royal-Mcbee

 * LGP-30
 * LGP-21

Sage Computer Technology

 * Sage II

Scientific Data Systems

 * SDS 940

SWTPC

 * SWTPC 6800

Systems Engineering Laboratories

 * SEL-32 both Concept-32 and PowerNode systems

Xerox Data Systems

 * Sigma