Computer Upgrade in the IUCF Control System

After 15 years of service and nine years of beam operation, the second generation Xerox Data Systems Sigma-2 computer has been replaced by a fourth generation Digital Equipment Corp. PDP-11/44 computer. Since all readout and control functions are performed via computer in the IUCF control system, this replacement affects all aspects of cyclotron operation. Whereas both hardware and software development may start from scratch because the old and new computers are of completely different architectures, the long history of cyclotron operation imposes some very strong constraints, particularly in the man-machine interface. Major design considerations and implementation features are outlined, along with operational experience to date.