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If there is a branch misprediction you have a penalty of 2 clock cycles. branch target buffer will help you only if you are predicting a branch as taken and it turns out so.

A branch target buffer is a buffer that is index by the branch instruction address with a tag for remaining bits. The info stored can be branch taken history and/or target address so it doesnt have to be recomputed.

can u tel me more abt branch target buffer

BTB is a special cache that stores the most recent used branch target addresses. Generally it has 32 locations. BTB and BPB are implemented in I-fetch stage. So we can get the target address and the direction of branch prediction in I-fetch stage, which reduces the penalty. If there is no BTB, we only can get the target address in decode stage. If a branch is predicted taken, we have to delay one cycle to get the target instruction.