Tru64 UNIX is a 64-bit UNIX operating system for the Alpha instruction set architecture, currently owned by Hewlett-Packard. Previously, Tru64 UNIX was a product of Compaq, and before that, Digital Equipment Corporation, where it was known as Digital UNIX. As its original name suggests, Tru64 UNIX is based on the OSF/1 operating system. DEC's previous UNIX product was known as Ultrix and was based on BSD. It is unusual among commercial UNIX implementations, as it is built on top of the Mach kernel developed at Carnegie Mellon University. Tru64 UNIX requires the SRM boot firmware found on Alpha-based computer systems.
Tru64 UNIX Popularity Over Time