Windows NT 3.1 is the first version of Windows NT. It was targeted for the Intel i860 CPU, but was ported to the MIPS platform in 1989 and to the Intel 386 in 1990. It was released for the Intel 386 and MIPS (MIPS64) platforms, and later on the DEC Alpha.
Its codename was NT OS/2 due to the fact that NT was initially going to be OS/2 3.0, but IBM and Microsoft split and developed NT on their own using parts off IBM's OS/2 operating system.
October 1991 Beta
December 1991 Beta
July 1992 Beta
October 1992 Beta
At least one of these builds also comes on 14 floppy disks.