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UCLA COMSCI M151B - hw1_sol

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Name: CSCE 212- Introduction to Computer ArchitectureSpring 2013- Homework 1Due date: 01/29/2012, In Class1. (10 points) Consider the following data for two different processors P1 and P2:Processor Clock Rate CPIP1 3GHz 1.5P2 2.5 GHz 1.0a) Which processor performs better? (Measure performance as instructions per second)Number of cycles per instructions P1 = 1.5Number of cycles per second P1 = 3 x 10^9Number of instructions per second P1 = 3 x 10^9 / 1.5 = 2 X 10^9Number of instructions per second P2 = 2.5 X 10^9/1 = 2.5 X 10^9 instructionsSince processer P2 executes more instructions per second, P2 is faster.b) If the processors each execute a program in 10 seconds, find the number of cycles and the number of instructions in the program.Execution time = CPI X IC / clock frequencyP1: 10 = 1.5 X IC / (3 X 10^9)IC = 2 X 10^10 instructionsCycles = 1.5 X 2 X 10^10 = 3 X 10^10P2: IC = 2.5 X 10^10 Cycles = 2.5 X 10^10 c) We are trying to reduce the time by 30% but this leads to an increase of 20% in CPI. What clock rate should we have to get this time reduction?P1: CPI = 1.2 X 1.5 = 1.8Say, original time was t then the new time is 0.7tLet the new frequency be f.0.7t = 1.8 X IC /ft = 1.5 X IC /(3GHz)0.7t/t = (1.8 X IC/f)/(1.5 X IC/3GHz)f = 5.14 GHzP2: f = 4.26 GHz2. (5 points) Suppose that we can improve the floating point instruction performance of machine by a factor of 15 (the same floating point instructions run 15 times faster on this new machine). What percent of the instructions must be floating point to achieve a Speedup of at least 4?Name: Speedup=1(1−α)+α /n = fraction speedup (to be calculated)n = speedup factor = 154=1(1−α)+α /15  = 0.803. (5 points) Assume that a design team is considering enhancing a machine by adding MMX (multimedia extension instruction) hardware to a processor. When a computation is run in MMX mode on the MMX hardware, it is 10 times faster than the normal mode of execution. Call the percentage of time that could be spent using the MMX mode the percentage of media enhancement. What percentage of media enhancement is needed to achieve an overall speedupof 2?2=1(1−α)+α /10  =


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UCLA COMSCI M151B - hw1_sol

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