system interface units

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1、ComputerArchitectureSystemInterfaceUnitsIolantheIIapproachesCoromandelHarbourSystemInterfaceUnit(alsoBusIU)Positionedbetweencacheandsystembus(externaltodie)SystemInterfaceUnit(alsoBusIU)CacheómainmemorybusResponsibleforMatchingcachelinelengthtomemorybusegPowerPC60132bytecacheline64bit(

2、8byte)busMemorytransactionsare“bursts”of4doublewordsGivingprioritytoreadsReadrequestsstallCPUpipelineWritesareassumed“complete”whentheyexitthepipelineDetectingreadsondatainthewritebuffersCachecoherence-later!SystemInterfaceUnitReadqueue2-4entriesReadwillfetchacacheline(PowerPC8words)Ne

3、edtofetchrequestedwordfirstMaybeword0-7inthecachelineBustransactionsmaybe“outoforder”RequestedwordfirstBusclock<

4、riesLowerprioritythanreadbufferAdditional(R10000)IncomingbufferExternalAgent(EA)supplyingdatawritestoitProcessordoesn’tcontroltransferEAsignalscompletionanddataforwardedtocacheUncachedbufferPagesmaybemarked“notcached”FasterI/OtransactionsSystemInterfaceUnitOverlapgreaterbusutilisatio

5、nSeparateAddressandDatabusesMultiplexingtwotypesofinformationonthesamebusSavespinsCoststime-unabletoassertbothatonceExpensiveforwrites!Requiredsince….wheneverSeparateAddressandDatabustenureAddressanddataphasessplitIssueaddress1,waitfordata1Issueaddress2whilewaitingfordata1PowerPCorgani

6、sationPowerPC601~1993BoundaryoftheSidieNew-Lookinthe“ExampleProcessors”sectionoftheWebnotesPowerPCorganisationPowerPC601~1993BoundaryoftheSidieNew-Lookinthe“ExampleProcessors”sectionoftheWebnotes3-waySuperScalarIntegerBranchFloatingPointPowerPCorganisationPowerPC601~1993BoundaryoftheSi

7、dieNew-Lookinthe“ExampleProcessors”sectionoftheWebnotesMMUUnifiedTLB(DataandI-misses)InstructionTLBPowerPCorganisationPowerPC601~1993BoundaryoftheSidieNew-Lookinthe“ExampleProcessors”sectionoftheWebnotesCacheUnified(DataandInst)PowerPCorganisationPowerPC601~1993BoundaryoftheSidieNew-