In the 1990s, and to some extent even in the new millennium, Unix was the standard when companies wanted to run business-critical applications in a fail-safe and high-performance manner but did not want to use a mainframe. IBM, Hewlett-Packard and Sun Microsystems were the most important providers, with SGI playing a marginal role. Each of these providers had their own Unix variant and their own RISC processor architecture. At best, x86 servers were used as file and print servers or for simple departmental tasks.

Most of what is still running on Unix systems today are customised, business-critical workloads in sectors such as financial services, healthcare and some industrial groups. It is too expensive and risky to migrate these applications, says Bowers. Unix programmes will probably still be around in 20 years' time.