Lecture05-06+-+Performance+II - EE207 Computer Organization Architecture Lecture 05 Measuring Performance II 1 MIPS as a Performance Measure MIPS

Lecture05-06+-+Performance+II - EE207 Computer Organization...

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1 EE207 Computer Organization & Architecture Lecture # 05 - Measuring Performance II
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MIPS: Millions Instructions Per Second Sometimes used as performance metric Faster machine larger MIPS MIPS specifies instruction execution rate We can also relate execution time to MIPS MIPS as a Performance Measure Instruction Count Execution Time × 10 6 Clock Rate CPI × 10 6 MIPS = = Inst Count MIPS × 10 6 Inst Count × CPI Clock Rate Execution Time = =
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Drawbacks of MIPS Three problems using MIPS as a performance metric 1. Does not take into account the capability of instructions Cannot use MIPS to compare computers with different instruction sets because the instruction count will differ 2. MIPS varies between programs on the same computer A computer cannot have a single MIPS rating for all programs 3. MIPS can vary inversely with performance A higher MIPS rating does not always mean better performance Example in next slide shows this anomalous behavior
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Two different compilers are being tested on the same program for a 4 GHz machine with three different classes of instructions: Class A, Class B, and Class Cwhich require 1, 2, and 3 cycles, respectively.The instruction count produced by the first compiler is 5 billion Class A instructions, 1 billion Class B instructions, and 1 billion Class C instructions.The second compiler produces 10 billion Class A instructions, 1 billion Class B instructions, and 1 billion Class C instructions.Which compiler produces a higher MIPS?Which compiler produces a better execution time?MIPS example ,
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