Components of CPU Performance

Components of CPU Performance - 02-1 02-1

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Unformatted text preview: 02-1 02-1 ComponentsofCPUPerformanceandPerformanceEquation Whyismycomputerfast(orslow)? Wouldithelptoimprove ? CPUperformanceequation isonewaytostartansweringthesequestions. 02-1 EE4720LectureTransparency.Formatted10:24,21January2004fromlsli02. 02-1 02-2 02-2 CPUPerformanceDecomposedintoThreeComponents: • ClockFrequency ( φ ) Determinedbytechnologyandinfluencedbyorganization. • ClocksperInstruction (CPI) DeterminedbyISA,microarchitecture,compiler,andprogram. • InstructionCount (IC) Determinedbyprogram,compiler,andISA. Thesecombinedtoform CPUPerformanceEquation t T = 1 φ × CPI × IC , where t T denotestheexecutiontime. 02-2 EE4720LectureTransparency.Formatted10:24,21January2004fromlsli02. 02-2 02-3 02-3 CPUPerformance:SimpleSystem Executioninprogramorder ... ... oneatatime. Instr. 1 Instr. 2 Instr. 3 Time/cycles: Time/mms: 1 2 3 4 5 6 7 8 9 10 11 80 160 Instr. 500,000 1,999,996 39,999,920 IC=500 , 000; φ =50kHz; CPI=4. Executiontime:IC × CPI. × clockperiod. Here( andonlyhere) CPIisnumberofcyclesforeachinstruction. 02-3 EE4720LectureTransparency.Formatted10:24,21January2004fromlsli02. 02-3 02-4 02-4 Execution:Pipelined,InOrder ToRunFaster:OverlapInstructions (PipelinedExecution) Resultmustbesameasone-at-a-timeexecution ... ... nottoodifficulttoachieve. Instr. 1 Instr. 2 Instr. 3 Time/cycles: Time/mms: 1 2 3 4 5 6 7 8 9 10 11 20 40 Instr. 500,000 750,000 3,750,000 Instr. 4 Instr. 5 Instr. 6 Instr. 7 IC=500 , 000; φ =200kHz; CPI= 750000 500000 =1 . 5. Executiontimeatbest:IC × clockperiod ... ... assuming1cycletostarteachinstructionand ... ... instructioncanstarteachcycle.(Slowerinillustration.) 02-4 EE4720LectureTransparency.Formatted10:24,21January2004fromlsli02. 02-4 02-5 02-5 Execution:Pipelined,IdealOutofOrder ToRunEvenFaster:OverlapInstructionsandStartOutofOrder Sometimesskipaninstructionandexecuteitlater. Instr. 1 Instr. 2 Instr. 3 Time/cycles: Time/mms: 1 2 3 4 5 6 7 8 9 10 11 4 8 Instr. 500,000 500,000 500,000 Instr. 4 Instr. 5 Instr. 6 Instr. 7 Instr. 8 Instr. 9 IC=500 , 000; φ =200kHz; CPI=1. Executiontimeatbest:IC × clockperiod ... ... assuming1cycletostarteachinstruction ... ... instructioncanstarteachcycle. 02-5 EE4720LectureTransparency.Formatted10:24,21January2004fromlsli02. 02-5 02-6 02-6 Execution:Pipelined,IdealOutofOrder,Superscalar ToRunFastest 1 :Overlap,Out-of-Order,Start n perTick( n-WaySuperscalar ). Requiresabout n timesasmuchhardware.(Below, n =2.) Instr. 1 Instr. 2 Instr. 3 Time/cycles: Time/mms: 1 2 3 4 5 6 7 8 9 10 11 .008 .016 Instr. 500,000 250,000 500 Instr. 4 Instr. 5 Instr. 6 Instr. 7 Instr. 8 Instr. 9 Instr. 12 Instr. 14 Instr. 15 Instr. 13 Instr. 10 Instr. 16 Instr. 11 Instr. 17 Instr. 18 IC=500 , 000; φ =500MHz; CPI= 1 2 . Executiontimeatbest: 1 n × IC × clockperiod ... ... assuming1cycletostarteachinstructioninstructioncanstarteachcycle. 1 Usingaconventionalserialinstructionsetarchitecture. 02-6 EE4720LectureTransparency.Formatted10:24,21January2004fromlsli02. 02-6 02-7 02-7 Execution:Pipelined,OutofOrder,Superscalar...
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This note was uploaded on 08/01/2009 for the course EE 4720 taught by Professor Staff during the Spring '08 term at LSU.

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Components of CPU Performance - 02-1 02-1

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