Raccolta domande teoriche anno 201718

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Advanced Computer Architectures Lorenzo Norcini Guglielmo Menchetti Alessio Russo Introito Tommaso Scarlatti Politecnico di Milano Contents 1 Questions 3 1.1 Why can’t an instruction enter the issue stage if it might cause a WAR or WAW hazard even if the earlier instruction causing the hazard has already started execution? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 Define control hazards and explain the main static branch prediction tech- niques used to solve them. What are the main advantages and disadvantages? Why superscalar processors use dynamic branch prediction instead ? . . . . . 4 1.3 Define the concept of precise exception . . . . . . . . . . . . . . . . . . . . . 5 1.4 Explain why exceptions can occur out of order in an in-order, 5-stage pipeline, describe how such a pipeline reorders these exceptions to provide a precise exception model. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.5 What is the main measure of performance for computer architects and why? Define the performance equation and define for each term what are the archi- tectural characteristics that impact on it. . . . . . . . . . . . . . . . . . . . . 6 1.6 Describe the main characteristics of VLIW architectures, showing advantages and disadvantages with respect to architectures based on dynamic scheduling. 7 1.7 Define the concepts of static scheduling and dynamic scheduling. What are the main advantages and disadvantages of the two classes of scheduling? . . 8 1.8 Write the formula of the Amdahl’s law and Explain the basic concepts ex- pressed by the Amdahl’s law . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 1.9 Describe the reasons why the instruction execution can become OUT OF ORDER in dynamic scheduling . . . . . . . . . . . . . .…