Use of OPEN systems for control, analysis and data acquisition of the DIII-D tokamak

For the past several years, it has been evident that the very old MODCOMP 18-bit computers being used at DIII-D for control and data acquisition were no longer adequate to perform the services needed. In early 1992, the computer systems group began to look seriously into alternate systems to replace these aged MODCOMP systems. The decision was made to investigate 'OPEN' system computers and also to maintain the compatibility with our large usage of CAMAC equipment as the real-time hardware interface. Information about the needs for real-time capabilities and 'OPEN' systems ability to meet these needs will be discussed. The needs include hardware requirements, operating system software which has known response rates, interconnectability and access of data from other workstations and computers. Some of the parameters and pitfalls of open systems will be discussed as well as the advantages of OPEN systems for use in a real-time environment. Our success at arriving at an OPEN systems solution will be examined.