SYSTEM FOR USING A DATA HISTORY TABLE TO SELECT AMONG MULTIPLE DATA PREFETCH ALGORITHMS

A prefetch unit stores a plurality of prefetch control fields in a data history table. Each prefetch control field selects one of multiple prefetch algorithms for use in prefetching data. As an instruction stream is fetched, the fetch address is provided to the data history table for selecting a prefetch control field. Since multiple prefetch algorithms are supported, many different data reference patterns may be prefetched. The prefetch unit is configured to gauge the effectiveness of the selected prefetch algorithm, and to select a different prefetch algorithm if the selected prefetch algorithm is found to be ineffective. The prefetch unit monitors the load/store memory operations performed in response to the instruction stream (i.e. the non-prefetch memory operations) to determine the effectiveness. Alternatively, the prefetch unit may evaluate each of the prefetch algorithms with respect to the observed set of memory references and select the algorithm which is most accurate.