SIMH is a

free and open source Free and open-source software (FOSS) is a term used to refer to groups of software consisting of both free software and open-source software where anyone is freely licensed to use, copy, study, and change the software in any way, and the sour ...

, multi-platform multi-system

emulator In computing, an emulator is hardware or software that enables one computer system (called the ''host'') to behave like another computer system (called the ''guest''). An emulator typically enables the host system to run software or use peri ...

. 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."Preserving Computing's Past: Restoration and Simulation"
Max Burnet and Bob Supnik, Digital Technical Journal, Volume 8, Number 3, 1996. SIMH was started in 1993 with the purpose of preserving

minicomputer A minicomputer, or colloquially mini, is a class of smaller general purpose computers that developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, ' ...

hardware and software that was fading into obscurity. In May 2022, the

MIT License The MIT License is a permissive free software license originating at the Massachusetts Institute of Technology (MIT) in the late 1980s. As a permissive license, it puts only very limited restriction on reuse and has, therefore, high license co ...

of SIMH version 4 on

GitHub GitHub, Inc. () is an Internet hosting service for software development and version control using Git. It provides the distributed version control of Git plus access control, bug tracking, software feature requests, task management, conti ...

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 BSD licenses are a family of permissive free software licenses, imposing minimal restrictions on the use and distribution of covered software. This is in contrast to copyleft licenses, which have share-alike requirements. The original BSD lice ...

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 BESM-6 (russian: БЭСМ-6, short for ''Большая электронно-счётная машина'', i.e. 'Large Electronic Calculating Machine') was a Soviet electronic computer of the BESM series. It was the first Soviet second-generation ...

Burroughs

* B5500

Control Data Corporation

CDC 1700 The CDC 1700 was a 16-bit word minicomputer, manufactured by the Control Data Corporation with deliveries beginning in May 1966. Over the years there were several versions. The original 1700 was constructed using air-cooled CDC 6600-like cordwood ...

Data General

Nova A nova (plural novae or novas) is a transient astronomical event that causes the sudden appearance of a bright, apparently "new" star (hence the name "nova", which is Latin for "new") that slowly fades over weeks or months. Causes of the dramat ...

Eclipse An eclipse is an astronomical event that occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three ce ...

Digital Equipment Corporation

Alpha Alpha (uppercase , lowercase ; grc, ἄλφα, ''álpha'', or ell, άλφα, álfa) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter aleph , w ...

PDP-1 The PDP-1 (''Programmed Data Processor-1'') is the first computer in Digital Equipment Corporation's PDP series and was first produced in 1959. It is famous for being the computer most important in the creation of hacker culture at Massachuset ...

PDP-4 The PDP-4 was the successor to the Digital Equipment Corporation's PDP-1. History This 18-bit machine, first shipped in 1962, was a compromise: "with slower memory and different packaging" than the PDP-1, but priced at $65,000 - less than half th ...

PDP-7 The PDP-7 was a minicomputer produced by Digital Equipment Corporation as part of the PDP series. Introduced in 1964, shipped since 1965, it was the first to use their Flip-Chip technology. With a cost of , it was cheap but powerful by the s ...

PDP-8 The PDP-8 is a 12-bit minicomputer that was produced by Digital Equipment Corporation (DEC). It was the first commercially successful minicomputer, with over 50,000 units being sold over the model's lifetime. Its basic design follows the pioneeri ...

PDP-9 The PDP-9, the fourth of the five 18-bit minicomputers produced by Digital Equipment Corporation, was introduced in 1966. A total of 445 PDP-9 systems were produced, of which 40 were the compact, low-cost PDP-9/L units.. History The 18-bit PDP ...

PDP-10 Digital Equipment Corporation (DEC)'s PDP-10, later marketed as the DECsystem-10, is a mainframe computer family manufactured beginning in 1966 and discontinued in 1983. 1970s models and beyond were marketed under the DECsystem-10 name, especi ...

PDP-11 The PDP-11 is a series of 16-bit minicomputers sold by Digital Equipment Corporation (DEC) from 1970 into the 1990s, one of a set of products in the Programmed Data Processor (PDP) series. In total, around 600,000 PDP-11s of all models were sold ...

PDP-15 The PDP-15 was the fifth and last of the 18-bit minicomputers produced by Digital Equipment Corporation. The PDP-1 was first delivered in December 1959 and the first PDP-15 was delivered in February 1970. More than 400 of these successors to th ...

* 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 __NOTOC__ Year 650 ( DCL) was a common year starting on Friday (link will display the full calendar) of the Julian calendar. The denomination 650 for this year has been used since the early medieval period, when the Anno Domini calendar era bec ...

* 701 *

704 __NOTOC__ Year 704 ( DCCIV) was a leap year starting on Tuesday (link will display the full calendar) of the Julian calendar. The denomination 704 for this year has been used since the early medieval period, when the Anno Domini calendar era be ...

1401 Year 1401 ( MCDI) was a common year starting on Saturday (link will display the full calendar) of the Julian calendar. Events January–December * January 6 – Rupert, King of Germany, is crowned King of the Romans at Cologne. * ...

1620 Events January–June * February 4 – Prince Bethlen Gabor signs a peace treaty with Ferdinand II, Holy Roman Emperor. * May 17 – The first merry-go-round is seen at a fair (Philippapolis, Turkey). * June 3 – Th ...

* 1130 * 7010 * 7070 * 7080 * 7090/7094 *

System/3 The IBM System/3 was an IBM midrange computer introduced in 1969, and marketed until 1985. It was produced by IBM Rochester in Minnesota as a low-end business computer aimed at smaller organizations that still used IBM 1400 series computers or ...

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 The Altair 8800 is a microcomputer designed in 1974 by Micro Instrumentation and Telemetry Systems, MITS and based on the Intel 8080 central processing unit, CPU. Interest grew quickly after it was featured on the cover of the January 1975 issue o ...

both

Intel 8080 The Intel 8080 (''"eighty-eighty"'') is the second 8-bit microprocessor designed and manufactured by Intel. It first appeared in April 1974 and is an extended and enhanced variant of the earlier 8008 design, although without binary compatibil ...

and

Zilog Z80 The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first working samples were ...

versions

Royal-Mcbee

LGP-30 The LGP-30, standing for Librascope General Purpose and then Librascope General Precision, was an early off-the-shelf computer. It was manufactured by the Librascope company of Glendale, California (a division of General Precision Inc.), and ...

* LGP-21

Sage Computer Technology

* Sage II

Scientific Data Systems

* SDS 940

SWTPC

* SWTPC 6800

Xerox Data Systems

Sigma Sigma (; uppercase Σ, lowercase σ, lowercase in word-final position ς; grc-gre, σίγμα) is the eighteenth letter of the Greek alphabet. In the system of Greek numerals, it has a value of 200. In general mathematics, uppercase Σ is used as ...

References

External links

* *
Additional VAX/MicroVAX models for SIMH

Debian Package

FreeBSD Port

UNIX: Old School. Using SIMH to explore UNIX history - Matthew Hoskins
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