ee488_Amdahls_law

# ee488_Amdahls_law - system – A Upgrade CPU with new...

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N orthwestern P olytechnic U niversity EE488 Lecture Notes Amdahl’s Law

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Amdahl’s Law EE488 - NPU 1967 George Amdahl compared the relationship of all components to the overall system efficiency. This was summarized in the formula… Formula states that the speedup (S) improvement depends on both the speedup of the particular component to how frequently that component is used. s = speedup f = fraction of usage of enhanced component k = speedup of new component + = k f f S ) 1 ( 1 formula is known as Amdahl’s Law
Amdahl’s Law EE488 - NPU Assume you analyze an application running on a system and observe that 70% of the time the application runs out of the CPU and 30% of the time it accesses the disk. The IT group provides two options to update the current

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Unformatted text preview: system. – A) Upgrade CPU with new processor array that cost \$10,000 and will provide a 50% performance increase. – B) Upgrade the disk drives for \$7,000 and will 2.5x performance increase. • Which is the best option from pure \$ per performance increase? Amdahl’s Law EE488 - NPU ( ) %) 130 ( 30 . 1 5 . 1 7 . ) 7 . 1 ( 1 5 . 1 , 7 . ≈ + − = = = s k f Option A) 130% for \$10,000 = 10,000/30 ~ \$333 per every 1% increase ( ) %) 122 ( 22 . 1 5 . 2 3 . ) 3 . 1 ( 1 5 . 2 , 3 . ≈ + − = = = s k f Option B) 122% for \$7,000 =7,000/22 ~ \$318 per every 1% increase All else being equal then the disk drives are best choice....
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ee488_Amdahls_law - system – A Upgrade CPU with new...

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