题目
题目

CS-6290-O01 Midterm

多项填空题

A processor is executing a long-running program, in which the most frequently executed branch instruction is encountered 8 million times per second. This branch has the following sequence of outcomes (where N stands for not-taken and T stands for taken): N, N, N, T, N, N, N, T, N, N, N, T, etc. In other words, this branch has a repeating pattern where it is not taken three times then taken once. For the first five occurrences of this branch instruction, the following table shows the counter values for the one-bit counter predictor, along with its predictions, and the actual branch outcomes (see above). Note that the counter starts out with an initial value of 1. Fill out the missing entries in the table: Note that the pattern has four branch occurrences while this table has five, i.e. the 5th occurrence of the branch in the table belongs to the second "round" of the pattern. Now suppose that we are measuring the accuracy of this branch during the third second of execution, i.e. after the predictor has already been trained by the first 16 million occurrences of this branch. To simplify things, you should assume that the predictor entries that are used for predicting this branch are only used for this branch, i.e. no other branches are interfering with the prediction, and that the initial values of all bits in the predictor were zeroes - but note that these values have been updated during the first two seconds of execution. Based on this, complete the following statements (your answers should be numbers):

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The prompt you provided contains the full question text but the answer options are missing. Without the listed answer choices, I cannot perform option-by-option analysis as requested, i.e., I cannot identify which option is correct, nor explain why each provided option is right or wrong. What I can do is outline how to approach solving this kind of problem, and illustrate the reasoning for the underlying concepts, so you can apply it to the complete set of options once they’re available: - Restate the question clearly: We’re dealing with a one-bit branch predictor, a repeating 4-branch pattern (N, N, N, T), and the predictor starts with a counter value of 1 (which implies an initial prediction of Taken for the first prediction, since the typical encoding is ......Login to view full explanation

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