# hw1_sol2.docx - CSCE 614: Computer Architecture Spring 2019...

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CSCE 614: Computer ArchitectureSpring 2019Homework 1Assigned: Jan 24Due in classFeb/07Total points: 50Name:1.Amdahl’s law [8 points]Three enhancements with the following speedups are proposed for a new architecture:Speedup1= 30Speedup2= 20Speedup3= 10Only one enhancement is usable at a time.a)[4 points] If enhancements 1 and 2 are each usable for 30% of the time, whatfraction of the time must enhancement 3 be used to achieve an overall speedupof 10?
Grading:3points for correctly setting up the equation1points for the correct values in the equation and get the final answer.b)[4 points] Assume for some benchmark, the fraction of use is 15% for each ofenhancements 1 and 2 and 70% for enhancement 3. We want to maximizeperformance. If only one enhancement can be implemented, which should it be?If two enhancements can be implemented, which should be chosen?
Speedupfor two enhancements = [ 1 – (FE1+ FE2) + ( (FE1/SE1) + (FE2/SE2) ) ]-1If we plug in the numbers, we get:Speedup1= (1 – 0.15 + 0.15/30)-1= 1.169Speedup2= (1 – 0.15 + 0.15/20)-1= 1.166Speedup3= (1 – 0.70 + 0.70/10)-1= 2.703Therefore, if we are allowed to select a single enhancement, we would choose E3Speedup12= [(1 - 0.15 - 0.15) + (0.15/30 + 0.15/20)]-1= 1.4035Speedup13= [(1 - 0.15 - 0.70) + (0.15/30 + 0.70/10)]-1= 4.4444Speedup23= [(1 - 0.15 - 0.70) + (0.15/20 + 0.70/10)]-1= 4.3956Therefore, if two enhancements can be implemented, we would choose E1and E3.Grading:2 points for correctly calculating one enhancement speedups2 points for the correctly calculating two enhancement speedups

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