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NotesForMidterm2

NotesForMidterm2 - – time spent executing actual...

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MULTIPLICATION AND DIVISION Binary Multiplication × 0 1 0 0 0 1 0 1 Multiplication Implementation Division PERFORMANCE Throughput – How many results per clock? How many results can be processed per second? What is the average execution rate of my program?
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How much work (latency) is getting done? Latency – clocks from input to corresponding output How long does it take for my program to run? How long must I wait after typing return for the result? An upgrade with a faster processor improves throughput Design Tradeoffs Maximum Performance (instructions per second) Minimum Cost (size of circuit) Best Performance/Price(ration of MIPS to size) Execution Time – Elapsed Time/Wall Clock Time Counts everything (disk and memory accesses, I/O, etc.) A useful number, but often not good for comparison purposes CPU time – Doesn’t include I/O or time spent running other programs Can be broken up into system time and user time Instruction Count * CPI / Clock Rate Our Focus: User CPU Time
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Unformatted text preview: – time spent executing actual instructions of “our” program Performance – Performance = Program Executions/Time (executions/sec) X is n times faster than Y means Performance X / Performance Y = n Clock Cycles Cycle Time – time between ticks = seconds per cycle Clock Rate – cycles per second (frequency) Computer Performance Measure How To Improve Performance cycle time (seconds per cycle) clock rate (cycles per second) CPI (average clocks per instruction) a floating point intensive application might have a higher CPI MIPS (millions of instructions per second) this would be higher for a program using simple instructions CPI Freq IPS M = cycle second program cycles program seconds × = Benchmarks Performance best determined by running a real application SPEC (System Performance Evaluation Cooperative) Amdahl’s Law unaffecte speedup affected improved t r t t + =...
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