Merge is a

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consist ...

system which allows a user to run

DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...

Windows 3.1 Windows 3.1 is a major release of Microsoft Windows. It was released to manufacturing on April 6, 1992, as a successor to Windows 3.0. Like its predecessors, the Windows 3.1 series ran as a shell on top of MS-DOS. Codenamed Janus, Windows ...

SCO UNIX Xinuos OpenServer, previously SCO UNIX and SCO Open Desktop (SCO ODT), is a closed source computer operating system developed by Santa Cruz Operation (SCO), later acquired by SCO Group, and now owned by Xinuos. Early versions of OpenServer were ...

, in an

8086 The 8086 (also called iAPX 86) is a 16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released. The Intel 8088, released July 1, 1979, is a slightly modified chip with an external 8-bit data bus (allo ...

virtual machine In computing, a virtual machine (VM) is the virtualization/ emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized h ...

History

Merge was originally developed to run

under

UNIX System V Unix System V (pronounced: "System Five") is one of the first commercial versions of the Unix operating system. It was originally developed by AT&T and first released in 1983. Four major versions of System V were released, numbered 1, 2, 3, an ...

Release 2 on an AT&T 6300 Plus personal computer. Development of the virtual machine began in late 1984, and AT&T announced the availability of the machine on 9 October 1985, referring to the bundled Merge software as Simultask. (The PC 6300 Plus shipped with

MS-DOS MS-DOS ( ; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few o ...

in 1985 though, because its Unix System V distribution was not ready until the end March 1986.) Merge was developed by engineers at

Locus Computing Corporation Locus Computing Corporation was formed in 1982 by Gerald J. Popek, Charles S. Kline and Gregory I. Thiel to commercialize the technologies developed for the LOCUS distributed operating system at UCLA. Locus was notable for commercializing s ...

, with collaboration from AT&T hardware and software engineers, particularly on aspects of the system that were specific to the 6300 Plus (in contrast to a standard

IBM PC/AT The IBM Personal Computer/AT (model 5170, abbreviated as IBM AT or PC/AT) was released in 1984 as the fourth model in the IBM Personal Computer line, following the IBM PC/XT and its IBM Portable PC variant. It was designed around the Intel 80 ...

). The AT&T 6300 Plus contained an

Intel 80286 The Intel 80286 (also marketed as the iAPX 286 and often called Intel 286) is a 16-bit microprocessor that was introduced on February 1, 1982. It was the first 8086-based CPU with separate, non- multiplexed address and data buses and also the ...

processor, which did not include the support for

virtual machines (

virtual 8086 mode In the 80386 microprocessor and later, virtual 8086 mode (also called virtual real mode, V86-mode, or VM86) allows the execution of real mode applications that are incapable of running directly in protected mode while the processor is running a ...

) found in the

80386 The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistorsrealmode. The 6300 Plus was designed with special hardware on the bus that would suppress and capture bus cycles from the DOS program if they were directed toward addresses not assigned for direct access by the DOS virtual machine. Various system registers, such as the programmable interrupt controller (PIC), and the video controller, had to be emulated in software for the DOS process, and a

watchdog timer A watchdog timer (sometimes called a ''computer operating properly'' or ''COP'' timer, or simply a ''watchdog'') is an electronic or software timer that is used to detect and recover from computer malfunctions. Watchdog timers are widely used in ...

was implemented to recover from DOS programs that would clear the interrupt flag and then hang for too long. The hardware used the

non-maskable interrupt In computing, a non-maskable interrupt (NMI) is a hardware interrupt that standard interrupt-masking techniques in the system cannot ignore. It typically occurs to signal attention for non-recoverable hardware errors. Some NMIs may be masked, but ...

(NMI) to take control back to the emulation code. Later, Merge was enhanced to make use of the

provided by the 80386 processor; that version was offered with

Microport MicroPort is a global medical device developer and manufacturer that is headquartered in Shanghai, China. It designs and produces products for a range of medical fields including cardiology, interventional radiology, orthopedics, electrophysiolog ...

SVR3 starting in 1987, and subsequently with

SCO Unix Xinuos OpenServer, previously SCO UNIX and SCO Open Desktop (SCO ODT), is a closed source computer operating system developed by Santa Cruz Operation (SCO), later acquired by SCO Group, and now owned by Xinuos. Early versions of OpenServer were ...

. There was also a Merge/286 version that ran on an unmodified PC/AT (without any special I/O trapping hardware); it ran as long as the PC program was reasonably well-behaved, though a malicious or crashing program could take the unprotected UNIX kernel down on those machines. Even so, the notoriously ill-behaved

Microsoft Flight Simulator ''Microsoft Flight Simulator'' is a series of amateur flight simulator programs for Microsoft Windows operating systems, and earlier for MS-DOS and Classic Mac OS. It was an early product in the Microsoft application portfolio and differed sig ...

would run on the PC/AT simultaneously with Unix. These later versions were marketed directly by Locus as well as through some OEM and ISV channels. A product-evaluation version with user manual appeared in January 1987, with retail Version 1.0 of Merge/386 shipping in October of that year. In the late 1980s, the main commercial competitor of Merge was VP/IX developed by

Interactive Systems Corporation Interactive Systems Corporation (styled INTERACTIVE Systems Corporation, abbreviated ISC) was a US-based software company and the first vendor of the Unix operating system outside AT&T, operating from Santa Monica, California. It was founded in 19 ...

and

Phoenix Technologies Phoenix Technologies Ltd is an American company that designs, develops and supports core system software for personal computers and other computing devices. The company's products commonly referred to as BIOS (Basic Input/Output System) or firm ...

. AT&T's Simultask 2.0 was based on VP/IX. In 1992,

Univel Univel, Inc. was a joint venture of Novell and AT&T's Unix System Laboratories (USL) that was formed in December 1991 to develop and market the Destiny desktop Unix operating system, which was released in 1992 as UnixWare 1.0. Univel existed ...

UnixWare 1.0 Personal Edition came with ''DOS Merge 3.0'' and

Novell Novell, Inc. was an American software and services company headquartered in Provo, Utah, that existed from 1980 until 2014. Its most significant product was the multi- platform network operating system known as Novell NetWare. Under the le ...

's DR DOS 6.0. Locus eventually joined the

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washi ...

WISE program which gave them access to

Microsoft Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...

source code, which allowed later versions of Merge to run Windows ''shrink wrapped'' applications without a copy of Windows. On 12 April 1995, Platinum Technology announced an agreement in principle to acquire Locus Computing Corporation for approximately million, about 1/4 of which was attributed to the Merge technology and product. The acquisition went through, and Platinum went on to develop the SCO Merge 4 version with

Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft as part of its Windows 9x family of operating systems. The first operating system in the 9x family, it is the successor to Windows 3.1x, and was released to manufacturi ...

support, which was released in 1998. The Merge technology was bought by a company called DASCOM in 1999, which was in turn bought by IBM. A company called TreLOS was spun off in 2000 that continued the development of the virtual machine software and created

Win4Lin Win4Lin is a discontinued proprietary software application for Linux which allowed users to run a copy of Windows 9x, Windows 2000 or Windows XP applications on their Linux desktop. Win4Lin was based on Merge software, a product which changed owne ...

. TreLOS later merged into NeTraverse, Inc. The

SCO Group The SCO Group (often referred to SCO and later called The TSG Group) was an American software company in existence from 2002 to 2012 that became known for owning Unix operating system assets that had belonged to the Santa Cruz Operation (the o ...

distributes NeTraverse Merge 5.3, which supports their current products

SCO OpenServer Xinuos OpenServer, previously SCO UNIX and SCO Open Desktop (SCO ODT), is a closed source computer operating system developed by Santa Cruz Operation (SCO), later acquired by SCO Group, and now owned by Xinuos. Early versions of OpenServer wer ...

5.x and UnixWare 7.

References

External links

* * {{Unix–Windows interoperability Virtualization software

History

See also

References

External links