AIX Version 1, introduced in 1986 for the IBM 6150 RT workstation, was based on UNIX System V Releases 1 and 2. In developing AIX, IBM and INTERACTIVE Systems Corporation (whom IBM contracted) also incorporated source code from 4.2 and 4.3BSD UNIX.
Among other variants, IBM later produced AIX Version 3 (also known as AIX/6000), based on System V Release 3, for their IBM POWER-based RS/6000 platform. Since 1990, AIX has served as the primary operating system for the RS/6000 series (later renamed IBM eServer pSeries, then IBM System p, and now IBM Power Systems). AIX Version 4, introduced in 1994, added symmetric multiprocessing with the introduction of the first RS/6000 SMP servers and continued to evolve through the 1990s, culminating with AIX 4.3.3 in 1999. Version 4.1, in a slightly modified form, was also the standard operating system for the Apple Network Server systems sold by Apple Computer to complement the Macintosh line.
In the late 1990s, under Project Monterey, IBM and the Santa Cruz Operation planned to integrate AIX and UnixWare into a single 32-bit/64-bit multiplatform UNIX with particular emphasis on running on Intel IA-64 (Itanium) architecture CPUs. A beta test version of AIX 5L for IA-64 systems was released, but according to documents released in SCO vs. IBM, less than forty licenses for the finished Monterey Unix were ever sold before the project was terminated in 2002.
AIX 6 was announced in May 2007 and ran an open beta from June 2007 until the general availability (GA) of AIX 6.1 on November 9th, 2007. Major new features in AIX 6.1 included full role-based access control, workload partitions (which enable application mobility), enhanced security (Addition of AES encryption type for NFS v3 and v4) and live partition mobility on the POWER6 hardware.