《电子信息工程专业英语导论》课件PART_2_unit5.ppt

PART2ModernElectronicsDevicesUNIT5ThebasiccomponentsofcomputersystemHowasystemdesignsthesepartsimpactsthesystemperformance.InVNAmachines,likethe80x86family,theCPUiswherealltheactionstakeplace[1].
[1].在VNA机器体系中，如8086系列，CPU是执行所有事务的地方。
在theCPUiswherealltheactionstakeplace中，主语是theCPU，wherealltheactionstakeplace是关系副词where引导的从句充当表语。
AllcomputationsoccurinsidetheCPU.ThesystembusconnectsvariouscomponentsofaVNAmachine.The80x86familyhasthreemajorbusses:theaddressbus,thedatabus,andthecontrolbus.Abusisaconnectionofwiresonwhichelectricalsignalspassthroughcomponentsinthesystem.
Forexample,thedatabusmayhaveadifferentimplementationbetweenthe80386andthe8086,Theonlyquestionis,“WhichmemorylocationorI/Odevice?”Theaddressbusanswersthisquestion.
TodifferentiatememorylocationandI/Odevice,auniquememoryaddressisassignedtoeachmemoryelementandI/Odevice.WhenthesoftwarewantstoaccesscertainmemorylocationorI/Odevice,itplacesthecorrespondingaddressontheaddressbus.Thecontrolbusisacollectionofsignalsthatcontrolshowtheprocessorcommunicateswiththerestofthesystem[3].
[3].控制总线是控制处理器与系统其他部分通信的信号枢纽。
thatcontrolshowtheprocessorcommunicateswiththerestofthesystem是定语从句，修饰主语thecontrolbus，在这个从句中，又包含了how引导的从句作为controls的宾语。
Theexactstructureofcontrolbusvariesamongprocessorsinthe80x86family.However,somecontrollinesarecommontoallprocessorsandareworthyabriefmention.
Thereadlineandwritelinecontrolthedirectionofdataonthedatabus.Ifthewritelineislow,thesystemtransfersdatafromtheCPUtomemory.
Themainmemoryisthecentralstorageunitinacomputersystem.Itisarelativelylargeandfastmemoryusedtostoreprogramsanddataduringthecomputeroperation.Theprincipaltechnologyusedforthemainmemoryisbasedonsemiconductorintegratedcircuit.IntegratedcircuitRAM(ReadRandomMemory)chipisavailableintwopossibleoperationmodes,staticanddynamic.ThestaticRAMconsistsessentiallyofinternalflip-flopsthatstorethebinaryinformation.Thestoredinformationremainsvalidaslongaspowerisappliedtotheunit.ThedynamicRAMstoresthebinaryinformationintheformofelectricchargethatisappl