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This paper presents a real-time scheduling methodology in a semiconductor wafer fab that produces multiple product types with different due dates. In the suggested real-time scheduling method, lot scheduling rules and batch scheduling rules are selected from sets of candidate rules based on information obtained from discrete event simulation. Since a rule combination that gives the best performance may vary according to the states of the fab, a selected rule combination is employed for a certain period of time and then a new combination is selected and employed. Since multiple simulation runs should be made in the simulation-based real-time scheduling (SBRTS) method, it may take excessively long computation time to react to unexpected events. To reduce response time, we suggest three techniques for accelerating rule comparison. We test these techniques as well as other operational policies that can be used in the SBRTS method through computational experiments on a number of test problems.