A model of a multiprocessing, multiprogramming computer system with serially reusable programs was developed to study the effect of serial programs on system performance. Two strategies for implementing serially reusable programs were investigated, a wait strategy in which the processor waits until the serial program is available, and a switch strategy, in which the processor is freed to do other work. Relative performances and asymptotic conditions as functions of the number of processors, processes, serially reusable programs, and the fraction of time each process executes serially reusable programs were obtained. Quantitative results are presented showing that the switch strategy is superior. The wait strategy causes quick saturation when the number of processes is increased.
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