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ProgressinComputersPrestigeLecturedeliveredtoIEE,Cambridge,on5February2004MauriceWilkesComputerLaboratoryUniversityofCambridgeThefirststoredprogramcomputersbegantoworkaround1950.TheonewebuiltinCambridge,theEDSACwasfirstusedinthesummerof1949.Theseearlyexperimentalcomputerswerebuiltbypeoplelikemyselfwithvaryingbackgrounds.Weallhadextensiveexperienceinelectronicengineeringandwereconfidentthatthatexperiencewouldstandusingoodstead.Thisprovedtrue,althoughwehadsomenewthingstolearn.Themostimportantofthesewasthattransientsmustbetreatedcorrectly;whatwouldcauseaharmlessflashonthescreenofatelevisionsetcouldleadtoaseriouserrorinacomputer.Asfarascomputingcircuitswereconcerned,wefoundourselveswithanembarassderichess.Forexample,wecouldusevacuumtubediodesforgatesaswedidintheEDSACorpentodeswithcontrolsignalsonbothgrids,asystemwidelyusedelsewhere.Thissortofchoicepersistedandthetermfamiliesoflogiccameintouse.ThosewhohaveworkedinthecomputerfieldwillrememberTTL,ECLandCMOS.Ofthese,CMOShasnowbecomedominant.Inthoseearlyyears,theIEEwasstilldominatedbypowerengineeringandwehadtofightanumberofmajorbattlesinordertogetradioengineeringalongwiththerapidlydevelopingsubjectofelectronics.dubbedintheIEElightcurrentelectricalengineering.properlyrecognisedasanactivityinitsownright.Irememberthatwehadsomedifficultyinorganisingaconferencebecausethepowerengineers’waysofdoingthingswerenotourways.AminorsourceofirritationwasthatallIEEpublishedpaperswereexpectedtostartwithalengthystatementofearlierpractice,somethingdifficulttodowhentherewasnoearlierpracticeConsolidationinthe1960sBythelate50sorearly1960s,theheroicpioneeringstagewasoverandthecomputerfieldwasstartingupinrealearnest.Thenumberofcomputersintheworldhadincreasedandtheyweremuchmorereliablethantheveryearlyones.Tothoseyearswecanascribethefirststepsinhighlevellanguagesandthefirstoperatingsystems.Experimentaltime-sharingwasbeginning,andultimatelycomputergraphicswastocomealong.Aboveall,transistorsbegantoreplacevacuumtubes.Thischangepresentedaformidablechallengetotheengineersoftheday.Theyhadtoforgetwhattheyknewaboutcircuitsandstartagain.Itcanonlybesaidthattheymeasuredupsuperblywelltothechallengeandthatthechangecouldnothavegonemoresmoothly.Soonitwasfoundpossibletoputmorethanonetransistoronthesamebitofsilicon,andthiswasthebeginningofintegratedcircuits.Astimewenton,asufficientlevelofintegrationwasreachedforonechiptoaccommodateenoughtransistorsforasmallnumberofgatesorflipflops.Thisledtoarangeofchipsknownasthe7400series.Thegatesandflipflopswereindependentofoneanotherandeachhaditsownpins.Theycouldbeconnectedbyoff-chipwiringtomakeacomputeroranythingelse.Thesechipsmadeanewkindofcomputerpossible.Itwascalledaminicomputer.Itwassomethinglessthatamainframe,butstillverypowerful,andmuchmoreaffordable.Insteadofhavingoneexpensivemainframeforthewholeorganisation,abusinessorauniversitywasabletohaveaminicomputerforeachmajordepartment.Beforelongminicomputersbegantospreadandbecomemorepowerful.Theworldwashungryforcomputingpowerandithadbeenveryfrustratingforindustrynottobeabletosupplyitonthescalerequiredandatareasonablecost.Minicomputerstransformedthesituation.Thefallinthecostofcomputingdidnotstartwiththeminicomputer;ithadalwaysbeenthatway.ThiswaswhatImeantwhenIreferredinmyabstracttoinflationinthecomputerindustry‘goingtheotherway’.Astimegoesonpeoplegetmorefortheirmoney,notless.ResearchinComputerHardware.ThetimethatIamdescribingwasawonderfuloneforresearchincomputerhardware.Theuserofthe7400seriescouldworkatthegateandflip-floplevelandyettheoveralllevelofintegrationwassufficienttogiveadegreeofreliabilityfarabovethatofdiscreettransistors.Theresearcher,inauniversityorelsewhere,couldbuildanydigitaldevicethatafertileimaginationcouldconjureup.IntheComputerLaboratorywebuilttheCambridgeCAP,afull-scaleminicomputerwithfancycapabilitylogic.The7400serieswasstillgoingstronginthemid1970sandwasusedfortheCambridgeRing,apioneeringwide-bandlocalareanetwork.PublicationofthedesignstudyfortheRingcamejustbeforetheannouncementoftheEthernet.Untilthesetwosystemsappeared,usershadmostlybeencontentwithteletype-basedlocalareanetworks.Ringsneedhighreliabilitybecause,asthepulsesgorepeatedlyroundthering,theymustbecontinuallyamplifiedandregenerated.Itwasthehighreliabilityprovidedbythe7400seriesofchipsthatgaveusthecourageneededtoembarkontheprojectfortheCambridgeRing.TheRISCMovementandItsAftermathEarlycomputershadsimpleinstructionsets.Astimewentondesignersofcommerciallyavailablemachinesaddedadditionalfeatureswhichtheythoughtwouldimproveperformance.Fewcomparativemeasurementsweredoneandonthewholethechoiceoffeaturesdependeduponthedesigner’sintuition.In1980,theRISCmovementthatwastochangeallthisbrokeontheworld.ThemovementopenedwithapaperbyPattersonandDitzelentitledTheCasefortheReducedInstructionsSetComputer.Apartfromleadingtoastrikingacronym,thistitleconveyslittleoftheinsightsintoinstructionsetdesignwhichwentwiththeRISCmovement,inparticularthewayitfacilitatedpipelining,asystemwherebyseveralinstructionsmaybeindifferentstagesofexecutionwithintheprocessoratthesametime.P