Virtual Labs

What is the primary function of a branch predictor in a CPU pipeline?

a: To increase the clock speed of the processor. Explanation

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b: To reduce the number of branch instructions in a program. Explanation

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c: To guess the outcome of a conditional branch instruction. Explanation

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d: To store the results of arithmetic operations. Explanation

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How does a one-bit branch predictor make its prediction?

a: It always predicts 'taken'. Explanation

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b: It uses the result of the last execution of the same branch. Explanation

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c: It analyzes the instruction that follows the branch. Explanation

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d: It uses a random number generator. Explanation

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What are the two states of a one-bit branch predictor?

a: Start and End Explanation

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b: Taken and Not Taken Explanation

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c: Correct and Incorrect Explanation

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d: Read and Write Explanation

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What is the main limitation of a one-bit branch predictor, especially in a loop?

a: It always mispredicts the first and last iterations. Explanation

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b: It is too complex to implement in hardware. Explanation

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c: It consumes too much power. Explanation

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d: It can only predict forward branches. Explanation

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How many bits does a two-bit saturating counter use for prediction?

a: 1 Explanation

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b: 2 Explanation

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c: 3 Explanation

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d: 4 Explanation

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In a two-bit predictor, which state transition occurs when a branch is in the 'Strongly Taken' (11) state and the branch is not taken?

a: It remains in the 'Strongly Taken' (11) state. Explanation

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b: It moves to the 'Weakly Taken' (10) state. Explanation

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c: It moves to the 'Weakly Not Taken' (01) state. Explanation

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d: It moves to the 'Strongly Not Taken' (00) state. Explanation

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Why is a two-bit predictor generally more accurate than a one-bit predictor?

a: It can predict the direction of the branch. Explanation

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b: It requires two consecutive mispredictions to change its prediction. Explanation

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c: It is faster at making predictions. Explanation

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d: It uses a more complex algorithm. Explanation

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Consider a two-bit predictor in the 'Weakly Not Taken' (01) state. What happens if the next two branches are taken?

a: It moves to 'Strongly Taken' (11). Explanation

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b: It moves to 'Weakly Taken' (10). Explanation

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c: It remains in 'Weakly Not Taken' (01). Explanation

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d: It moves to 'Strongly Not Taken' (00). Explanation

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Which of the following sequences of branch outcomes would result in the highest accuracy for a one-bit predictor, starting in the 'Not Taken' state?

a: T, N, T, N, T, N Explanation

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b: T, T, T, T, T, T Explanation

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c: N, N, N, N, N, N Explanation

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d: T, T, N, N, T, T Explanation

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One-Two Bit Branch Prediction