It is unusual among commercial UNIX implementations, as it is built on top of the Mach kernel developed at Carnegie Mellon University.

(Other UNIX and UNIX-like implementations built on top of the Mach kernel are GNU Hurd, NeXTSTEP, MkLinux, and Darwin.)

In 1988, Digital Equipment Corporation (DEC) joined with IBM, Hewlett-Packard, and others to form the Open Software Foundation (OSF).

A primary aim was to develop a version of Unix, named OSF/1, to compete with System V Release 4 from AT&T Corporation and Sun Microsystems.

[5] A Chinese version of Tru64 UNIX named COSIX was jointly developed by Compaq and China National Computer Software & Technology Service Corporation (CS&S).

With their purchase of Compaq in 2002, HP announced their intention to migrate many of Tru64 UNIX's more innovative features (including its AdvFS, TruCluster, and LSM) to HP-UX.