IBM on Monday will release z/OS, its z900 mainframe operating system upgraded to take advantage of the new model's 64bit design. Z/OS is a major overhaul of the basic software that runs the mainframe, a traditional computing design with a decades-old lineage. Z/OS, along with Linux, are the two major software initiatives designed to restore the mainframe's relevance in an age when Unix servers from companies such as Sun Microsystems have stolen most of the high-end server momentum. The new version of the operating system, formerly called OS/390 to match the previous S/390 mainframe product name, offers a number of new features. Among them is the ability to use a storage space with a 64bit address, which IBM said speeds communications with the memory system and transactions with databases compared with the older 32bit technology. Z/OS also includes the Intelligent Resource Director, which lets the computer quickly and automatically shift resources to jobs that require more power. The new operating system also has better support for Sun's Java software and Linux, two technologies that make writing software for a mainframe easier for modern programmers. And IBM promises z/OS makes it easier to set up and administer a mainframe, a significant change in light of how expensive the mainframes are to run. As Microsoft has found with Windows 2000 and Apple with Mac OS X, overhauling operating systems is very hard even with forgiving customers. Mainframe customers, though, are a notoriously conservative and demanding bunch. To justify prices soaring well over $1m, mainframes offer several high-end features. Among them are the ability to conduct very fast transactions with a database and the ability to be split into several independent partitions, each with its own operating system. Unix servers from Sun, Compaq, IBM and Hewlett-Packard have been emulating those features on lower-priced systems, but still haven't caught up. IBM's mainframes weigh between one and two tons apiece. The first version of z/OS, V1R1, will be available Friday, IBM said. A later revision to z/OS, V1R2, is expected in October, IBM said. That will include new features such as an internal network technology called "HiperSockets" that lets one partition communicate with another at a much higher speed than the regular computer network. Though z/OS will run on earlier G5 and G6 mainframe models, it won't be able to take advantage of features of the newer z900, which had been code-named "Freeway" and still is sometimes called by the moniker G7. Among those features are the 64bit address space, HiperSockets and the Intelligent Resource Director. IBM also is in the midst of overhauling how it charges for mainframe software. In the past, it charged based on the total computing power of the system. The company is changing to a new model in which it charges only for the computing power of the partition in which the software is running. IBM began updating its mainframe pricing scheme last July as a way to make it less costly to try out Linux software. Take me to ZDNet Enterprise Have your say instantly, and see what others have said. Click on the TalkBack button and go to the ZDNet News forum. Let the editors know what you think in the Mailroom. And read what others have said.