06 04 2022 E S Santambrogio

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Dipartimento di Elettronica e Informazione Politecnico di Milano 20133 Milano (Italia) Piazza Leonardo da Vinci, 32 Tel. (+39) 02-2399.3400 Fax (+39) 02-2399.3411 Advanced Computer Architecture April 06, 2022 Prof. Donatella Sciuto and Marco Santambrogio Name Last Name Professor: You’ll have 15’ to complete the exam Problem 1 (25% aka 1pt) Problem 2 (25% aka 1pt) Problem 3 (25% aka 1pt) Problem 4 (25% aka 1pt) Total (100%) Problem 1 Which of the following statements about branch prediction are FALSE? We may have more than a single FALSE statement. Only correct answers will be counted for the score. Answer 1: The behavior of each branch is always assumed independent from other branches (FALSE) Answer 2: Branch prediction can only happen at compile time (FALSE) Answer 3: Different techniques can be combined in order to improve prediction accuracy Answer 4: Profile-Driven is an example of a static branch predictor Answer 1 Different techniques make different assumptions in order to make a prediction, for example an n-bit-BHT only considers the history of the branch to be predicted (with n regulating how much of the past history to consider). An (m,n) Correlating Branch predictor on the other hand, takes into account the behavior of the last m branches. Branch prediction can happen both at compile time (static) or during the execution (dynamic), the two approaches we briefly described above are examples of dynamic branch prediction techniques while Profile-Driven or Delayed Branch are static predictors. Static predictions may be used to assist dynamic predictors. Problem 2 The “Branch Always Taken” technique is not applicable to the five-stage MIPS pipeline! Is this statement true or false? Answer1: True Answer2: False Answer 2 Because we used “applicable” in the question,…