Apparatus and method of throttling hardware pre-fetch

Hardware based prefetching for processor systems is implemented. A prefetch unit can be provided in a cache subsystem that allocates a prefetch tracker in response to a demand request for a cache line that missed. In response to subsequent demand requests to consecutive cachelines, a confidence indicator is increased. In response to further demand misses and a confidence indicator value, a prefetch tier is increased, which allows the prefetch tracker to initiate prefetch requests for more cachelines. Requests for cachelines that are more than two cachelines apart within a match window for the allocated prefetch tracker decreases the confidence faster than requests for consecutive cachelines increase confidence. An age counter tracks when a last demand request within the match window was received. The prefetch tier can be decreased in response to reduced confidence and increased age.