A/UX is Apple Inc.'s implementation of the Unix operating system for some of their Apple Macintosh computers, the latest versions running on the Mac II, Quadra and Centris series of machines. A/UX was first released in 1988, with the final version (3.1.1) released in 1995. A/UX requires a Motorola 680x0 Mac with an FPU and a paged memory management unit (PMMU). The system is based on System V.2.2 with features of V.3 and V.4 and BSD 4.2 and 4.3. It is POSIX and System V Interface Definition (SVID) compliant. Aside from a few isolated servers, this OS is essentially extinct.