Models for Parallel Processing WIthin Programs: Application to CPU:I/O and I/O:I/O Overlap Approximate queueing models for internal parallel processing by individual programs in a multiprogrammed system are developed in this paper. The solution technique is developed by network decomposition. The models are formulated in terms of CPU:I/O and I/O:I/O overlap and applied to the analysis of these problems. The percentage performance improvement from CPU:I/O overlap is found to be greatest for systems which are in approximate CPU:I/O utilization balance and for low degrees of multiprogramming. The percentage improvement from I/O:I/O overlap is found to be greatest for systemtems in which the I/O system is more utilized than the CPU. CACM October, 1978 Towsley, D. Chandy, K. Browne, J. Multiprogramming, parallel processing, queueing network models, multiprocessing of computation and I/O 4.32 8.1 CA781002 DH January 29, 1979 6:23 PM 3059 4 3059 3070 4 3059 1685 5 3059 2988 5 3059 3059 5 3059 3059 5 3059 3059 5 3059 3059 6 3059