计算机英语CPU.docx
- 文档编号:7974250
- 上传时间:2023-01-27
- 格式:DOCX
- 页数:14
- 大小:136.88KB
计算机英语CPU.docx
《计算机英语CPU.docx》由会员分享,可在线阅读,更多相关《计算机英语CPU.docx(14页珍藏版)》请在冰豆网上搜索。
计算机英语CPU
Centralprocessingunit
DieofanIntel80486DX2microprocessor(actualsize:
12×6.75 mm)initspackaging.
Thecentralprocessingunit(CPU)istheportionofacomputersystemthatcarriesouttheinstructionsofacomputerprogram,andistheprimaryelementcarryingoutthecomputer'sfunctions.Thecentralprocessingunitcarriesouteachinstructionoftheprograminsequence,toperformthebasicarithmetical,logical,andinput/outputoperationsofthesystem.Thistermhasbeeninuseinthecomputerindustryatleastsincetheearly1960s.[1]Theform,designandimplementationofCPUshavechangeddramaticallysincetheearliestexamples,buttheirfundamentaloperationremainsmuchthesame.
EarlyCPUswerecustom-designedasapartofalarger,sometimesone-of-a-kind,computer.However,thiscostlymethodofdesigningcustomCPUsforaparticularapplicationhaslargelygivenwaytothedevelopmentofmass-producedprocessorsthataremadeforoneormanypurposes.Thisstandardizationtrendgenerallybeganintheeraofdiscretetransistormainframesandminicomputersandhasrapidlyacceleratedwiththepopularizationoftheintegratedcircuit(IC).TheIChasallowedincreasinglycomplexCPUstobedesignedandmanufacturedtotolerancesontheorderofnanometers.BoththeminiaturizationandstandardizationofCPUshaveincreasedthepresenceofthesedigitaldevicesinmodernlifefarbeyondthelimitedapplicationofdedicatedcomputingmachines.Modernmicroprocessorsappearineverythingfromautomobilestocellphonesandchildren'stoys.
Contents
[hide]
∙1History
o1.1DiscretetransistorandintegratedcircuitCPUs
o1.2Microprocessors
∙2Operation
∙3Designandimplementation
o3.1Integerrange
o3.2Clockrate
o3.3Parallelism
▪3.3.1Instructionlevelparallelism
▪3.3.2Thread-levelparallelism
▪3.3.3Dataparallelism
∙4Performance
∙5Seealso
∙6Notes
∙7References
∙8Externallinks
History
Mainarticle:
HistoryofgeneralpurposeCPUs
EDVAC,oneofthefirstelectronicstoredprogramcomputers.
ComputerssuchastheENIAChadtobephysicallyrewiredinordertoperformdifferenttasks,whichcausedthesemachinestobecalled"fixed-programcomputers."Sincetheterm"CPU"isgenerallydefinedasasoftware(computerprogram)executiondevice,theearliestdevicesthatcouldrightlybecalledCPUscamewiththeadventofthestored-programcomputer.
Theideaofastored-programcomputerwasalreadypresentinthedesignofJ.PresperEckertandJohnWilliamMauchly'sENIAC,butwasinitiallyomittedsothemachinecouldbefinishedsooner.OnJune30,1945,beforeENIACwascompleted,mathematicianJohnvonNeumanndistributedthepaperentitledFirstDraftofaReportontheEDVAC.Itoutlinedthedesignofastored-programcomputerthatwouldeventuallybecompletedinAugust1949.[2]EDVACwasdesignedtoperformacertainnumberofinstructions(oroperations)ofvarioustypes.TheseinstructionscouldbecombinedtocreateusefulprogramsfortheEDVACtorun.Significantly,theprogramswrittenforEDVACwerestoredinhigh-speedcomputermemoryratherthanspecifiedbythephysicalwiringofthecomputer.ThisovercameaseverelimitationofENIAC,whichwastheconsiderabletimeandeffortrequiredtoreconfigurethecomputertoperformanewtask.WithvonNeumann'sdesign,theprogram,orsoftware,thatEDVACrancouldbechangedsimplybychangingthecontentsofthecomputer'smemory.
WhilevonNeumannismostoftencreditedwiththedesignofthestored-programcomputerbecauseofhisdesignofEDVAC,othersbeforehim,suchasKonradZuse,hadsuggestedandimplementedsimilarideas.Theso-calledHarvardarchitectureoftheHarvardMarkI,whichwascompletedbeforeEDVAC,alsoutilizedastored-programdesignusingpunchedpapertaperatherthanelectronicmemory.ThekeydifferencebetweenthevonNeumannandHarvardarchitecturesisthatthelatterseparatesthestorageandtreatmentofCPUinstructionsanddata,whiletheformerusesthesamememoryspaceforboth.MostmodernCPUsareprimarilyvonNeumannindesign,butelementsoftheHarvardarchitecturearecommonlyseenaswell.
Asadigitaldevice,aCPUislimitedtoasetofdiscretestates,andrequiressomekindofswitchingelementstodifferentiatebetweenandchangestates.Priortocommercialdevelopmentofthetransistor,electricalrelaysandvacuumtubes(thermionicvalves)werecommonlyusedasswitchingelements.Althoughthesehaddistinctspeedadvantagesoverearlier,purelymechanicaldesigns,theywereunreliableforvariousreasons.Forexample,buildingdirectcurrentsequentiallogiccircuitsoutofrelaysrequiresadditionalhardwaretocopewiththeproblemofcontactbounce.Whilevacuumtubesdonotsufferfromcontactbounce,theymustheatupbeforebecomingfullyoperational,andtheyeventuallyceasetofunctionduetoslowcontaminationoftheircathodesthatoccursinthecourseofnormaloperation.Ifatube'svacuumsealleaks,assometimeshappens,cathodecontaminationisaccelerated.Usually,whenatubefailed,theCPUwouldhavetobediagnosedtolocatethefailedcomponentsoitcouldbereplaced.Therefore,earlyelectronic(vacuumtubebased)computersweregenerallyfasterbutlessreliablethanelectromechanical(relaybased)computers.
TubecomputerslikeEDVACtendedtoaverageeighthoursbetweenfailures,whereasrelaycomputerslikethe(slower,butearlier)HarvardMarkIfailedveryrarely.[1]Intheend,tubebasedCPUsbecamedominantbecausethesignificantspeedadvantagesaffordedgenerallyoutweighedthereliabilityproblems.MostoftheseearlysynchronousCPUsranatlowclockratescomparedtomodernmicroelectronicdesigns(seebelowforadiscussionofclockrate).Clocksignalfrequenciesrangingfrom100kHzto4 MHzwereverycommonatthistime,limitedlargelybythespeedoftheswitchingdevicestheywerebuiltwith.
DiscretetransistorandintegratedcircuitCPUs
CPU,corememory,andexternalbusinterfaceofaDECPDP-8/I.madeofmedium-scaleintegratedcircuits
ThedesigncomplexityofCPUsincreasedasvarioustechnologiesfacilitatedbuildingsmallerandmorereliableelectronicdevices.Thefirstsuchimprovementcamewiththeadventofthetransistor.TransistorizedCPUsduringthe1950sand1960snolongerhadtobebuiltoutofbulky,unreliable,andfragileswitchingelementslikevacuumtubesandelectricalrelays.WiththisimprovementmorecomplexandreliableCPUswerebuiltontooneorseveralprintedcircuitboardscontainingdiscrete(individual)components.
Duringthisperiod,amethodofmanufacturingmanytransistorsinacompactspacegainedpopularity.Theintegratedcircuit(IC)allowedalargenumberoftransistorstobemanufacturedonasinglesemiconductor-baseddie,or"chip."Atfirstonlyverybasicnon-specializeddigitalcircuitssuchasNORgateswereminiaturizedintoICs.CPUsbaseduponthese"buildingblock"ICsaregenerallyreferredtoas"small-scaleintegration"(SSI)devices.SSIICs,suchastheonesusedintheApolloguidancecomputer,usuallycontainedtransistorcountsnumberinginmultiplesoften.TobuildanentireCPUoutofSSIICsrequiredthousandsofindividualchips,butstillconsumedmuchlessspaceandpowerthanearlierdiscretetransistordesigns.Asmicroelectronictechnologyadvanced,anincreasingnumberoftransistorswereplacedonICs,thusdecreasingthequantityofindividualICsneededforacompleteCPU.MSIandLSI(medium-andlarge-scaleintegration)ICsincreasedtransistorcountstohundreds,andthenthousands.
In1964IBMintroduceditsSystem/360computerarchitecturewhichwasusedinaseriesofcomputersthatcouldrunthesameprogramswithdifferentspeedandperformance.Thiswassignificantatatimewhenmostelectroniccomputerswereincompatiblewithoneanother,eventhosemadebythesamemanufacturer.Tofacilitatethisimprovement,IBMutilizedtheconceptofamicroprogram(oftencalled"microcode"),whichstillseeswidespreadusageinmodernCPUs.[3]TheSystem/360architecturewassopopularthatitdominatedthemainframecomputermarketfordecadesandleftalegacythatisstillcontinuedbysimilarmoderncomputersliketheIBMzSeries.Inthesameyear(1964),DigitalEquipmentCorporation(DEC)introducedanotherinfluentialcomputeraimedatthescientificandresearchmarkets,thePDP-8.DECwouldlaterintroducetheextremelypopularPDP-11linethatoriginallywasbuiltwithSSIICsbutwaseventuallyimplementedwithLSIcomponentsoncethesebecamepractical.InstarkcontrastwithitsSSIandMSIpredecessors,thefirstLSIimplementationofthePDP-11containedaCPUcomposedofonlyfourLSIintegratedcircuits.[4]
Transistor-basedcomputershadseveraldistinctadvantagesovertheirpredecessors.Asidefromfacilitatingincreasedreliabilityandlowerpowerconsumption,transistorsalsoallowedCPUstooperateatmuchhigherspeedsbecauseoftheshortswitchingtimeofatransistorincomparisontoatubeorrelay.Thankstoboththeincreasedreliabilityaswellasthedramaticallyincreasedspeedoftheswitchingelements(whichwerealmostexclusivelytransistorsbythistime),CPUclockratesinthetensofmegahertzwereobtainedduringthisperiod.AdditionallywhilediscretetransistorandICCPUswereinheavyusage,newhigh-performancedesignslikeSIMD(SingleInstructionMultipleData)vectorprocessorsbegantoappear.TheseearlyexperimentaldesignslatergaverisetotheeraofspecializedsupercomputerslikethosemadebyCrayInc.
Microprocessors
ThediefromanIntel8742
Intel80486DX2microprocessorinaceramicPGApackage.
Theintroductionofthemicroprocessorinthe1970ssignificantlyaffectedt
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- 计算机 英语 CPU