Merge (software)
Encyclopedia
Merge is a software system which allows a user to run DOS
/Windows 3.1
on SCO UNIX, in an 8086
virtual machine
.
Merge was originally developed to run DOS
under UNIX System V Release 2 on an AT&T 6300+ ("sixty-three hundred plus") personal computer. Development of the virtual machine began in late 1984, and AT&T announced the availability of the machine on October 9, 1985, referring to the bundled Merge software as SimulTask. Merge was developed by engineers at Locus Computing Corporation
, with collaboration from AT&T hardware and software engineers, particularly on aspects of the system that were specific to the 6300+ (in contrast to a standard PC/AT).
The AT&T 6300+ contained an Intel 80286
processor, which did not include the support for 8086
virtual machines (Virtual 8086 mode
) found in the Intel 80386
and later processors in the x86 family. On the 80286, the DOS program had to run in realmode. The 6300+ 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, and the video controller, had to be emulated in software for the DOS process, and a watchdog timer 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 (NMI) to take control back to the emulation code. More detail may be seen in the patent referenced in the External Links below.
Later Merge was enhanced to make use of the Virtual 8086 mode
provided by the Intel 80386
processor; that version was offered with Microport
SVR3 starting in 1987, and subsequently with SCO Unix
. 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
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.
Locus eventually joined the Microsoft
WISE
program which gave them access to Microsoft Windows
source code, which allowed later versions of Merge to run Windows Shrink wrapped applications without a copy of Windows.
On April 12, 1995, Platinum Technology
announced an agreement in principle to acquire Locus Computing Corporation
for approximately US$33 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
support.
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
. TreLOS later merged into NeTraverse, Inc.
The SCO Group
distributes NeTraverse Merge 5.3 which supports their current products SCO OpenServer
5.x and UnixWare
7.
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...
/Windows 3.1
Windows 3.1x
Windows 3.1x is a series of 16-bit operating systems produced by Microsoft for use on personal computers. The series began with Windows 3.1, which was first sold during March 1992 as a successor to Windows 3.0...
on SCO UNIX, in an 8086
Intel 8086
The 8086 is a 16-bit microprocessor chip designed by Intel between early 1976 and mid-1978, when it was released. The 8086 gave rise to the x86 architecture of Intel's future processors...
virtual machine
Virtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
.
Merge was originally developed to run DOS
DOS
DOS, short for "Disk Operating System", is an acronym for several closely related operating systems that dominated the IBM PC compatible market between 1981 and 1995, or until about 2000 if one includes the partially DOS-based Microsoft Windows versions 95, 98, and Millennium Edition.Related...
under UNIX System V Release 2 on an AT&T 6300+ ("sixty-three hundred plus") personal computer. Development of the virtual machine began in late 1984, and AT&T announced the availability of the machine on October 9, 1985, referring to the bundled Merge software as SimulTask. Merge was developed by engineers at Locus Computing Corporation
Locus Computing Corporation
Locus Computing Corporation was formed in 1982 by Gerald J. Popekto commercialize the technologies developed for the LOCUS distributed operating system at UCLA...
, with collaboration from AT&T hardware and software engineers, particularly on aspects of the system that were specific to the 6300+ (in contrast to a standard PC/AT).
The AT&T 6300+ contained an Intel 80286
Intel 80286
The Intel 80286 , introduced on 1 February 1982, was a 16-bit x86 microprocessor with 134,000 transistors. Like its contemporary simpler cousin, the 80186, it could correctly execute most software written for the earlier Intel 8086 and 8088...
processor, which did not include the support for 8086
Intel 8086
The 8086 is a 16-bit microprocessor chip designed by Intel between early 1976 and mid-1978, when it was released. The 8086 gave rise to the x86 architecture of Intel's future processors...
virtual machines (Virtual 8086 mode
Virtual 8086 mode
In the 80386 microprocessor and later, virtual 8086 mode allows the execution of real mode applications that are incapable of running directly in protected mode while the processor is running a protected mode operating system.VM86 mode uses a segmentation scheme identical to that of real mode In...
) found in the Intel 80386
Intel 80386
The Intel 80386, also known as the i386, or just 386, was a 32-bit microprocessor introduced by Intel in 1985. The first versions had 275,000 transistors and were used as the central processing unit of many workstations and high-end personal computers of the time...
and later processors in the x86 family. On the 80286, the DOS program had to run in realmode. The 6300+ 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, and the video controller, had to be emulated in software for the DOS process, and a watchdog timer 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 (NMI) to take control back to the emulation code. More detail may be seen in the patent referenced in the External Links below.
Later Merge was enhanced to make use of the Virtual 8086 mode
Virtual 8086 mode
In the 80386 microprocessor and later, virtual 8086 mode allows the execution of real mode applications that are incapable of running directly in protected mode while the processor is running a protected mode operating system.VM86 mode uses a segmentation scheme identical to that of real mode In...
provided by the Intel 80386
Intel 80386
The Intel 80386, also known as the i386, or just 386, was a 32-bit microprocessor introduced by Intel in 1985. The first versions had 275,000 transistors and were used as the central processing unit of many workstations and high-end personal computers of the time...
processor; that version was offered with Microport
Microport
Microport created the first version of AT&T UNIX System V for the IBM 286 and 386 Personal Computers, as well as IBM's PS/2 systems...
SVR3 starting in 1987, and subsequently with SCO Unix
SCO Group
TSG Group, Inc. is a software company formerly called The SCO Group, Caldera Systems, and Caldera International. After acquiring the Santa Cruz Operation's Server Software and Services divisions, as well as UnixWare and OpenServer technologies, the company changed its focus to UNIX...
. 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
Microsoft Flight Simulator is a series of flight simulator programs for the Microsoft Windows operating system, although it was marketed as a video game. It is one of the longest-running, best-known and most comprehensive home flight simulator series...
would run on the PC/AT simultaneously with Unix. These later versions were marketed directly by Locus
Locus Computing Corporation
Locus Computing Corporation was formed in 1982 by Gerald J. Popekto commercialize the technologies developed for the LOCUS distributed operating system at UCLA...
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.
Locus eventually joined the Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
WISE
Windows Interface Source Environment
Windows Interface Source Environment was a licensing program from Microsoft which allowed developers to recompile and run Windows-based applications on UNIX and Macintosh platforms....
program which gave them access to Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
source code, which allowed later versions of Merge to run Windows Shrink wrapped applications without a copy of Windows.
On April 12, 1995, Platinum Technology
Platinum Technology
Platinum Technology Inc. was founded by Andrew Filipowski in 1987 to market and support deployment of database management software products and the applications enabled by database management technology and render related services...
announced an agreement in principle to acquire Locus Computing Corporation
Locus Computing Corporation
Locus Computing Corporation was formed in 1982 by Gerald J. Popekto commercialize the technologies developed for the LOCUS distributed operating system at UCLA...
for approximately US$33 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
Windows 95 is a consumer-oriented graphical user interface-based operating system. It was released on August 24, 1995 by Microsoft, and was a significant progression from the company's previous Windows products...
support.
The Merge technology was bought by a company called DASCOM in 1999 which was in turn bought by IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
. A company called TreLOS was spun off in 2000 that continued the development of the virtual machine software and created Win4Lin
Win4Lin
Win4Lin was a proprietary software application for Linux which allowed users to run a copy of Microsoft Windows 95, 98, Me, 2000 or XP applications on their Linux desktop.-Overview:...
. TreLOS later merged into NeTraverse, Inc.
The SCO Group
SCO Group
TSG Group, Inc. is a software company formerly called The SCO Group, Caldera Systems, and Caldera International. After acquiring the Santa Cruz Operation's Server Software and Services divisions, as well as UnixWare and OpenServer technologies, the company changed its focus to UNIX...
distributes NeTraverse Merge 5.3 which supports their current products SCO OpenServer
SCO OpenServer
SCO OpenServer, previously SCO UNIX and SCO Open Desktop , is, misleadingly, a closed source version of the Unix computer operating system developed by Santa Cruz Operation and now maintained by the SCO Group....
5.x and UnixWare
UnixWare
UnixWare is a Unix operating system maintained by The SCO Group . UnixWare is typically deployed as a server rather than desktop. Binary distributions of UnixWare are available for x86 architecture computers. It was originally released by Univel, a jointly owned venture of AT&T's Unix System...
7.
See also
- Popek and Goldberg virtualization requirementsPopek and Goldberg virtualization requirementsThe Popek and Goldberg virtualization requirements are a set of conditions sufficient for a computer architecture to support system virtualization efficiently. They were introduced by Gerald J. Popek and Robert P. Goldberg in their 1974 article "Formal Requirements for Virtualizable Third...
(Dr. PopekGerald J. PopekGerald John "Jerry" Popek was an American computer scientist, known for his research on operating systems and virtualization.With Robert P...
was one of the founders of LocusLocus Computing CorporationLocus Computing Corporation was formed in 1982 by Gerald J. Popekto commercialize the technologies developed for the LOCUS distributed operating system at UCLA...
) - Windows Interface Source EnvironmentWindows Interface Source EnvironmentWindows Interface Source Environment was a licensing program from Microsoft which allowed developers to recompile and run Windows-based applications on UNIX and Macintosh platforms....