TWO-LEVEL BRANCH PREDICTION CACHE

摘要

An improved branch prediction cache (BPC) scheme that utilizes a hybrid cache structure. The BPC (13) provides two levels of branch information caching. The fully associative first level BPC (152) is a shallow but wide structure (36 32-byte entries), which caches full prediction information for a limited number of branch instructions. The second direct mapped level BPC (155) is a deep but narrow structure (256 2-byte entries), which caches only partial prediction information, but does so for a much larger number of branch instructions. As each branch instruction is fetched and decoded, its address is used to perform parallel look-ups in the two branch prediction caches.