Tru64 UNIX is a 64-bit UNIX operating system for the Alpha instruction set architecture (ISA), currently owned by Hewlett-Packard (HP). Previously, Tru64 UNIX was a product of Compaq, and before that, Digital Equipment Corporation (DEC), where it was known as Digital UNIX (formerly DEC OSF/1 AXP).
It is unusual among commercial UNIX implementations, as it is built on top of the Mach kernel developed at Carnegie Mellon University. (Other UNIX implementations built on top of the Mach kernel are NeXTSTEP, MkLinux, Mac OS X and Apple iOS.)
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. In December 2004, HP announced a change of plan: they would instead use the Veritas File System and abandon the Tru64 advanced features. In the process, many of the remaining Tru64 developers were laid off.
The current maintenance release, 5.1B-6 was released in October 2010.
In October 2010, HP stated that they would continue to support Tru64 UNIX until 31 December 2012.
In 1988, during the so-called “Unix wars“, DEC joined with IBM, Hewlett-Packard, and others to form the Open Software Foundation (OSF) to develop a version of Unix. Dubbed OSF/1, the aim was to compete with System V Release 4 from AT&T Corporation and Sun Microsystems, and it has been argued that a primary goal was for the operating system to be free of AT&T intellectual property. The fact that OSF/1 was one of the first operating systems to use the Mach kernel is cited as support of this assertion. Digital also strongly promoted OSF/1 for real-time applications, and with traditional UNIX implementations at the time providing poor real-time support at best, the real-time and multi-threading support was heavily dependent on the Mach kernel. It also incorporated a large part of the BSD kernel (based on the 4.3-Reno release) to provide Unix compatibility. OSF/1 was envisaged to be the third major branch of the Unix family tree, after System V and BSD.
DEC’s original release of OSF/1 (OSF/1 Release 1.0) was in January 1992 for their line of MIPS-based DECstation workstations, however this was never a fully supported product and was cancelled before the end of the year. DEC ported OSF/1 to their new Alpha AXP platform (as DEC OSF/1 AXP), and this was the first version (Release 1.2) of what is most commonly referred to as OSF/1. DEC OSF/1 AXP Release 1.2 was shipped on March 1993. OSF/1 AXP was a full 64-bit operating system and the native UNIX implementation for the Alpha architecture. From OSF/1 AXP V2.0 onwards, UNIX System V compatibility was also integrated into the system.
After Compaq’s purchase of DEC in early 1998, with the release of version 4.0F, Digital UNIX was renamed to Tru64 UNIX to emphasise its 64-bit-clean nature and de-emphasise the Digital brand.