What is the speedup of the basic pipeline (with branch predictions) shown in the Introduc- tion slides (Tsequential / Tpipelined) if 1/5 of all instructions are conditional branches and 4/5 of them are predicted incorrectly? Can you give a general formula for a k-stage pipeline? What other information do you need to know?

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What is the speedup of the pipeline if 1/5 of the instructions are branches, and 4/5 of those are correctly predicted? We have 100 instructions. Tsequential = 100 * 5 = 500 cycles Tpipelined Without stalls, they take 100 * 1 = 100 cycles 20 of them are branches 16 of them correctly predicted, incurring no additional stalls 4 of them are mispredicted, incurring 4 * 2 = 8 additional cycles Speedup = Tsequential/Tpipelined = 500 / (100+8) = 4.63