Microsoft and IBM were both developing OS/2 together. There were a lot of disagreements between the two companies. IBM wanted to keep supporting the 286. htt

Microsoft and IBM were both developing OS/2 together. There were a lot of disagreements between the two companies. IBM wanted to keep supporting the 286. https://en.wikipedia.org/wiki/OS/2#1990:_Breakup https://en.wikipedia.org/wiki/OS/2#1990:_Breakup > OS/2 1.x targets the Intel 80286 processor and DOS fundamentally does not. IBM insisted on supporting the 80286 processor, with its 16-bit segmented memory mode, because of commitments made to customers who had purchased many 80286-based PS/2s as a result of IBM's promises surrounding OS/2.[30] Until release 2.0 in April 1992, OS/2 ran in 16-bit protected mode and therefore could not benefit from the Intel 80386's much simpler 32-bit flat memory model and virtual 8086 mode features. This was especially painful in providing support for DOS applications. While, in 1988, Windows/386 2.1 could run several cooperatively multitasked DOS applications, including expanded memory (EMS) emulation, OS/2 1.3, released in 1991, was still limited to one 640 kB "DOS box". > Given these issues, Microsoft started to work in parallel on a version of Windows which was more future-oriented and more portable. The hiring of Dave Cutler, former VAX/VMS architect, in 1988 created an immediate competition with the OS/2 team, as Cutler did not think much of the OS/2 technology and wanted to build on his work on the MICA project at Digital rather than creating a "DOS plus". His NT OS/2 was a completely new architecture.[31] DOS extenders had started in the 1980's but they weren't a real OS but I would barely call DOS an OS either. https://en.wikipedia.org/wiki/DOS_extender https://en.wikipedia.org/wiki/DOS_extender But Unix was ported to the 386 in 1987. https://en.wikipedia.org/wiki/Xenix#Transfer_of_ownership_to_SCO https://en.wikipedia.org/wiki/Xenix#Transfer_of_ownership_to... > In 1987, SCO ported Xenix to the 386 processor, a 32-bit chip, after securing knowledge from Microsoft insiders that Microsoft was no longer developing Xenix.[41] Xenix System V Release 2.3.1 introduced support for i386, SCSI and TCP/IP. SCO's Xenix System V/386 was the first 32-bit operating system available on the market for the x86 CPU architecture. https://en.wikipedia.org/wiki/Xenix https://en.wikipedia.org/wiki/Xenix I had friends running Linux from the very beginning in 1991.