Exactly 40 years ago this week the IBM 360 was released, starting an era of mainframe computing which is currently enjoying a revival.

Unisys has seen sales of its ClearPath mainframe range growing over the past two years, and is today releasing three new models.

The company evolved out of Univac, which produced its first general purpose computer right back in 1952.

"From a security point of view, we have had zero damage due to viruses," said Chander Khanna, worldwide vice president of server platform marketing at Unisys.

Insurance firm Friends Provident, which has 30 years' experience of mainframes, switched from direct IBM support to value added reseller CSF in 2001 when it purchased an IBM Multiprize 3000.

"CSF gave us the same attention to detail of buying a system 10 times the size," Simon Rowlett, senior technical services manager at Friends Provident, told vnunet.com.

Friends Provident upgraded to an IBM z990 at the end of January, assisted by CSF, and is migrating a Java application to WebSphere on a z800 bought from CSF last year.

Bob Wilkie, zSeries sales manager at CSF, explained that he had seen a growth in mainframe usage since 2000.

"We started with very small companies. When IBM saw we were adding value, it brought us in to bigger ones. Now we deal with all but the big banks," he said.

The success of the mainframe is down to its availability, security and the arrival of Linux and Java applications.

Alan Mushett, managing director at Sionet International, which has been reselling and supporting Non-Stop mainframe systems for five years, said: "An absolute requirement is online accurate data which a mainframe provides.

"Users of a 24x7 technology expect us to offer the 24x7 mentality. We've got to be there for them."

Robert Wilkinson, server marketing manager at Unisys' strategic software group, added: "One survey showed that there was $55bn damage from viruses, with the biggest percentage from software overflow [code crossing between partitions].

"This cannot happen on our mainframes. If you cannot get insurance against a cyber-catastrophe, you ought to think of a mainframe."