An Analytic Model of the Hasp Execution Task Monitor The HASP Execution Task Monitor periodically rearranges the OS/360 dispatching chain to give tasks preemptive execution priority in inverse order to that of their cpu utilization history. The effect is to keep the I/O bound tasks active and to prevent cpu bound tasks from locking out other tasks. This paper develops a simple model of the Execution Task Monitor and employs it to study the effectiveness of the monitor in improving system performance. A modified strategy monitor control is investigated for the case of task execution in a memory hierarchy of varying speeds. CACM December, 1974 Strauss, J. C. Hasp, OS/360, dispatching, scheduling, modeling, performance evaluation 4.32 8.1 CA741203 JB January 16, 1978 9:51 AM 2571 4 2571 3072 4 2571 3119 4 2571 2245 5 2571 2571 5 2571 2571 5 2571 2571 5 2571