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INITIAL DEVELOPMENT NOMAD was developed by National CSS, Inc. , in Stamford, Connecticut , starting in 1973. It was made available only on NCSS's time-sharing system, VP/CSS . VP/CSS was a derivative of CP/CMS , the world's first fully virtual operating system, created at IBM 's Cambridge Scientific Center in Cambridge, Massachusetts . Serendipitously, CP/CMS was also the world's first successful " Open Source " project, since it was developed with US Government monies, and the source code was released in full to the public domain. The IBM 360/67 and subsequent IBM and IBM-clone architectures allowed for fully virtual operation by generating interrupts when privileged instructions were executed. This allowed CP to intercept and simulate those instructions, thus completely virtualizing the environment. Along with a few other timesharing vendors, National CSS noticed that the performance of the CMS single-user operating system that ran on top of the CP core could be significantly enhanced. This was done by replacing Channel Command Word s (CCWs) and other expensive simulated instructions with what are today called " BIOS Call s." It is enormously cheaper to make a direct trap for a targeted function than it is to simulate the operation of a complex I/O command (which was accomplished in CP/CMS's complex innermost core, in a routine called "CCWTRANS"). This hack enabled National CSS to build a version of CP/CMS, which it called "VP/CSS", that far outperformed IBM's own version of CP/CMS, which it branded as " VM/370 ." For example, VP routinely supported over 250 CSS users on hardware that could only support about 70 CMS users under VM. For reasons that are unclear, but may be related to IBM's primary emphasis on MVS and its successors as its core mainframe operating system, IBM ceded this massive advantage in performance to National CSS and others for many years, even though the optimization techniques to address the performance of CMS were well understood and well documented in the literature of the day. COMMERCIAL RELEASE The first customer usage of Nomad occurred in May 1975, but Nomad was first officially released in October 1975. Nomad competed principally with Focus and Ramis as it expanded its base, becoming available under VM in 1982 and under MVS in 1983. Versions were released under PC-DOS and Microsoft Windows in the late 1980s. OWNERSHIP Dun & Bradstreet acquired National CSS in and rebranded it as Dun & Bradstreet Computer Services or DBCS. In the assets of DBCS were sold to Must Software International of Norwalk, Connecticut (a wholly owned subsidiary of Thomson-CSF ) which became part of Thomson Software Products in 1995 and part of Aonix in 1996. As Of 2005 Nomad is sold and maintained by Select Business Solutions in Trumbull, Connecticut . |
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