TextChap1 - CSC 520 COMPUTER ARCHITECTURE Measuring...

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CSC 520 COMPUTER ARCHITECTURE Measuring Performance: Cannot compare performance using a single program Should use a “typical” workload Example: Given Computers: A B C Prog1 1 10 20 Prog2 1000 100 20 Overall 1001 110 40 The following are true: A is 10 times faster than B for Prog1 B is 10 times faster than A for Prog2 A is 20 times faster than C for Prog1 C is 50 times faster than A for Prog2 B is 2 times faster than C for Prog1 C is 5 times faster than B for Prog2 So what conclusion can you draw about relative performance?
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CSC 520 COMPUTER ARCHITECTURE Another look at Performance: May we conclude that C is the best computer for our application?
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CSC 520 COMPUTER ARCHITECTURE NO! We must consider our typical workload, how often is each program run? Using a weighted average is a much better method. Also, how much do the various computers cost?
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CSC 520 COMPUTER ARCHITECTURE AMDAHL’S LAW The performance improvement to be realized from using some faster mode of execution is limited by the fraction of time the faster mode can be used. “The performance improvement to be realized from improving some feature of a design is limited by the amount of time that feature is used and by the amount of improvement to the feature.” “Make the common case fast.” Amdahl’s Law thus defines the speedup that can be obtained by using a particular feature.
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CSC 520 COMPUTER ARCHITECTURE What is speedup? Performance for entire task using enhancement
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TextChap1 - CSC 520 COMPUTER ARCHITECTURE Measuring...

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