Unisys, one of the few companies remaining in the mainframe market, will begin selling a new high-end system Monday that includes features to run advanced software. The new ClearPath Plus Libra 185 comes with faster processors and more capacity for transferring data into and out of the system. As significant a change is the support for programs written using Microsoft's .Net infrastructure and Sun Microsystems' Java.

The move mirrors one that IBM, by far the dominant seller of mainframes today, has been making in recent years. Big Blue's WebSphere software provides a mechanism to develop and run complicated Java programs, while more recently the company has pushed a mainframe version of Linux to attract more programmers and software companies. Mainframes are large servers that typically feature strong reliability, high transaction processing power, and the ability to handle multiple jobs gracefully. Mainframes once were a vibrant, competitive market, but it was eroded by the advent of less-expensive machines that were good enough for many tasks. First came minicomputers from Digital Equipment, then Unix servers from Hewlett-Packard and Sun Microsystems, and now Windows and Linux servers from a variety of manufacturers.