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Mechanism for Recording Prefetching History in BHT Disclosure Number: IPCOM000038902D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01

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Bennett, BT Liu, L [+details]


In future high performance processors, prefetching of instruction cache lines is important for reducing instruction supply disruptions. The use of a Branch History Table (BHT) is a powerful mechanism for branch prediction and may be used to prefetch I-lines. Straightforward I-prefetching based on BHT decisions may, however, not reach decisions fast enough in order to overlap the time required to fetch a missed cache line. In this invention a mechanism is described in which the decision on which line is to be used next can be reached before an I-line is entered. The technique is to record prefetch information in BHT. In a typical BHT in which each entry records information, such as , where Branch represents a (taken ) Branch and Target represents the instruction (address) the branch is taken to.