高级计算机体系结构 9 存储器系统ppt课件.ppt

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1、Lecture9:MemorySystems:TechniquestoReduceMissesSpring2010SuperComputingLab.Review:DSPvs.GeneralPurposeMPUMIPS/MFLOPSofDSPs:speedofMultiply-Accumulate(MAC)DSPsarejudgedifkeepthemultipliersbusy100%The"SPEC"ofDSPsis4algorithms:InifiniteImpuleResponse(IIR)filtersFiniteI

2、mpuleResponse(FIR)filtersFFT,andconvolversInDSPs,algorithmsarekey!BinarycompatibilityisnotanissueSoftwareisnotkeyissueinDSPsPeoplestillwriteinassemblylanguageLibrariesveryimportantsodon’thavetowrite4algorithmsSomecallanythingtheywriteinassemblylanguagelibraryWhyMore

3、AboutMemoryHierarchy?ProcessorOnlyThusFarinCourse:CPUcost/performance,ISA,PipelinedExecutionProcessor-MemoryPerformanceGapMaxProcessor%Area%Transistors(Cost)(Power)Alpha2116437%77%StrongArmSA11061%94%PentiumPro64%88%2diesperpackage:Proc/I$/D$+L2$Cacheshavenoinherent

4、value,onlytrytocloseperformancegapReview:FourQuestionsforMemoryHierarchyDesignQ1:Wherecanablockbeplacedintheupperlevel?(Blockplacement)FullyAssociative,SetAssociative,DirectMappedQ2:Howisablockfoundifitisintheupperlevel?(Blockidentification)Tag/BlockQ3:Whichblocksh

5、ouldbereplacedonamiss?(Blockreplacement)Random,LRUQ4:Whathappensonawrite?(Writestrategy)WriteBackorWriteThrough(withWriteBuffer)Review:CachePerformanceCPUtime=(CPUexecutionclockcycles+Memorystallclockcycles)xclockcycletimeMemorystallclockcycles=(ReadsxReadmissratexR

6、eadmisspenalty+WritesxWritemissratexWritemisspenalty)Memorystallclockcycles=MemoryaccessesxMissratexMisspenaltyReview:CachePerformanceCPUtime=InstructionCountx(CPIexecution+MemaccessesperinstructionxMissratexMisspenalty)xClockcycletimeMissesperinstruction=Memoryacc

7、essesperinstructionxMissrateCPUtime=ICx(CPIexecution+MissesperinstructionxMisspenalty)xClockcycletimeReview:ImprovingCachePerformance1.Reducethemissrate,2.Reducethemisspenalty,or3.Reducethetimetohitinthecache.ReducingMissesClassifyingMisses:3CsCompulsory-Thefirstacc

8、esstoablockisnotinthecache,sotheblockmustbebroughtintothecache.Alsocalledcoldstartmissesorfirstreferencemisses.(MissesinevenanInfiniteCach