Multiple - Block Ahead

A basic rule in computer architecture is that a processor cannot execute an application faster than it fetches its instructions. This paper presents a novel cost-eeective mechanism called the two-block ahead branch predictor. Information from the current instruction block is not used for predicting the address of the next instruction block, but rather for predicting the block following the next instruction block. This approach overcomes the instruction fetch bottleneck exhibited by wide-dispatch \brainiac" processors by enabling them to eeciently predict addresses of two instruction blocks in a single cycle. Furthermore, pipelin-ing the branch prediction process can also be done by means of our predictor for \speed demon" processors to achieve higher clock rate or to improve the prediction accuracy by means of bigger prediction structures. Moreover, and unlike the previously-proposed multiple predictor schemes, multiple-block ahead branch pre-dictors can use any of the branch prediction schemes to perform the very accurate predictions required to achieve high-performance on superscalar processors.