Q42

A CPU has a five-stage pipeline and runs at $1$ GHz frequency. Instruction fetch happens in the first stage of the pipeline. A conditional branch instruction computes the target address and evaluates the condition in the third stage of the pipeline. The processor stops fetching new instructions following a conditional branch until the branch outcome is known. A program executes $10^9$ instructions out of which $20\%$ are conditional branches. If each instruction takes one cycle to complete on average, the total execution time of the program is: