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Experimentation aimed at determining the potential benefit of mixed-mode SIMD/MIMD parallel architectures is reported. The experimentation is based on timing measurements made on the PASM system prototype at Purdue utilizing carefully coded synthetic variations of a well-known algorithm. The syn-thetic algorithms used to measure and evaluate this system were based on the bitonic sorting of sequences stored in the processing elements. This computation was mapped to both the SIMD and MIMD modes of parallelism, as well as to two hybrids of the SIMD and MIMD modes. The computations were coded in these four ways and experiments that explore the trade-offs among them were performed. Consideration is given to the overhead caused by enabling or disabling PEs in SIMD mode and a lower bound on this overhead is shown. Finally, a more efficient PE mask generation scheme for multiple “off-the-shelf ” micropro-cessor-based SIMD systems is emulated and its performance is analyzed. The results of these experiments are presented and are discussed with special consideration of the effects of the sys-tem’s architecture. The goal is to (as much as possible) obtain implementation independent analyses of the attributes of mixed-mode parallel processing with respect to the computational characteristics of the application being examined. The results are used to gain insight into the impact of computation mode on synchronization and data-conditional aspects of system per-formance. 0 1991 Academic Press, Inc. 1