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Chapter 2. PC Components, Features, and System Design

Chapter 2. PC Components, Features, and System Design

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WhatIsaPC?

Inormallyaskthequestion,"WhatexactlyisaPC?"whenI

beginoneofmyPChardwareseminars.Ofcourse,mostpeople

immediatelyanswerthatPCstandsforpersonalcomputer,

whichinfactitdoes.Theymightthencontinuebydefininga

personalcomputerasanysmallcomputersystempurchased

andusedbyanindividual.Unfortunately,thatdefinitionisnot

nearlypreciseoraccurateenoughforourpurposes.Iagreethat

aPCisapersonalcomputer,butnotallpersonalcomputersare

PCs.Forexample,anAppleMacintoshsystemisclearlya

personalcomputer,butnobodyIknowwouldcallaMacaPC,

leastofallMacusers!ForthetruedefinitionofwhataPCis,

youmustlookdeeper.

CallingsomethingaPCimpliesthatitissomethingmuchmore

specificthanjustanypersonalcomputer.Onethingitimpliesis

afamilyrelationtotheoriginalIBMPCfrom1981.Infact,I'll

gosofarastosaythatIBMliterallyinventedthetypeof

computerwecallaPCtoday;thatis,IBMdesignedandcreated

theveryfirstone,andIBMoriginallydefinedandsetallthe

standardsthatmadethePCdistinctivefromotherpersonal

computers.Notethatitisveryclearinmymindaswellasinthe

historicalrecordthatIBMdidnotinventthepersonalcomputer.

(Mostrecognizethehistoricaloriginsofthepersonalcomputer

intheMITSAltair,introducedin1975.)So,IBMdidnotinvent

thepersonalcomputer,butitdidinventwhattodaywecallthe

PC.Somepeoplemighttakethisdefinitionastepfurtherand

defineaPCasanypersonalcomputerthatis"IBMcompatible."

Infact,manyyearsback,PCswerecalledeitherIBM

compatiblesorIBMclones,inessencepayinghomagetothe

originsofthePCatIBM.

TherealitytodayisthatalthoughIBMclearlydesignedand

createdthefirstPCin1981andcontrolledthedevelopmentand

evolutionofthePCstandardforseveralyearsthereafter,IBMis



nolongerincontrolofthePCstandard;thatis,itdoesnot

dictatewhatmakesupaPCtoday.IBMlostcontrolofthePC

standardin1987whenitintroduceditsPS/2lineofsystems.

Upuntilthen,othercompaniesthatwereproducingPCsliterally

copiedIBM'ssystemsrightdowntothechips;connectors;and

eventheshapes(formfactors)oftheboards,cases,andpower

supplies.After1987,IBMabandonedmanyofthestandardsit

createdinthefirstplace.That'swhyformanyyearsnowIhave

refrainedfromusingthedesignation"IBMcompatible"when

referringtoPCs.

IfaPCisnolongeranIBM-compatiblesystem,whatisit?The

realquestionseemstobe,"WhoisincontrolofthePCstandard

today?"Thatquestionisbestbrokendownintotwoparts.First,

whoisincontrolofPCsoftware?Second,whoisincontrolofPC

hardware?



WhoControlsPCSoftware?

Mostofthepeopleinmyseminarsdon'tevenhesitateforasplit

secondwhenIaskthisquestion;theyimmediatelyrespond,

"Microsoft!"Idon'tthinkthereisanyargumentwiththat

answer.Microsoftclearlycontrolstheoperatingsystemsused

onPCs,whichhavemigratedfromtheoriginalMS-DOSto

Windows3.1/95/98/Me,WindowsNT/2000,toWindowsXP.By

theendof2006,MicrosoftwillhavereleasedWindowsVista,

XP'seventualreplacement.

MicrosofthaseffectivelyuseditscontrolofthePCoperating

systemasleveragetoalsocontrolothertypesofPCsoftware,

suchasutilitiesandapplications.Forexample,manyutility

programsoriginallyofferedbyindependentcompanies,suchas

diskcaching,diskcompression,filedefragmentation,file

structurerepair,andevensimpleapplicationssuchascalculator

andnotepadprograms,arenowbundledin(includedwith)

Windows.Microsofthasevenbundledmorecomprehensive



applicationssuchasWebbrowsers,ensuringanautomatic

installedbasefortheseapplicationsmuchtothedismayof

companieswhoproducecompetingversions.Microsofthasalso

leverageditscontroloftheoperatingsystemtointegrateits

ownnetworkingsoftwareandapplicationssuitesmore

seamlesslyintotheoperatingsystemthanothers.That'swhyit

nowdominatesmostofthePCsoftwareuniverse,from

operatingsystemstonetworkingsoftwaretoutilities,fromword

processorstodatabaseprogramstospreadsheets.

IntheearlydaysofthePC,whenIBMwasclearlyincontrolof

thePChardwarestandard,ithiredMicrosofttoprovidemostof

thecoresoftwareforthePC.IBMdevelopedthehardware,

wrotethebasicinput/outputsystem(BIOS),andthenhired

Microsofttodevelopthediskoperatingsystem(DOS),aswell

asseveralotherprogramsandutilitiesforthePC.Inwhatwas

laterviewedasperhapsthemostcostlybusinessmistakein

history,IBMfailedtosecureexclusiverightstotheDOSithad

contractedfromMicrosoft,eitherbypurchasingitoutrightorby

anexclusivelicenseagreement.Instead,IBMlicensedit

nonexclusively,whichsubsequentlyallowedMicrosofttosellthe

sameMS-DOScodeitdevelopedforIBMtoanyothercompany

thatwasinterested.EarlyPCclonerssuchasCompaqeagerly

licensedthissameoperatingsystemcode,andsuddenly

consumerscouldpurchasethesamebasicMS-DOSoperating

systemwithseveraldifferentcompanynamesonthebox.In

retrospect,thatsinglecontractualerrormadeMicrosoftintothe

dominantsoftwarecompanyitistodayandsubsequently

causedIBMtolosecontroloftheveryPCstandardithad

created.

Asawritermyself(ofwords,notsoftware),Icanappreciate

whatanincredibleoversightthiswas.Imaginethatabook

publishercomesupwithagreatideaforaverypopularbook

andthencontractswithandsubsequentlypaysanauthorto

writeit.Then,byvirtueofapoorlywrittencontract,theauthor

discoversthathecanlegallyselltheverysamebook(perhaps



withadifferenttitle)toallthecompetitorsoftheoriginal

publisher.Ofcourse,nopublisherIknowwouldallowthisto

happen;yetthatisexactlywhatIBMallowedMicrosofttodo

backin1981.ByvirtueofitsdealwithMicrosoft,IBMhad

essentiallylostcontrolofthesoftwareitcommissionedforits

newPCfromdayone.

ItisinterestingtonotethatinthePCbusiness,softwareenjoys

copyrightprotection,whereashardwarecanbeprotectedonly

bypatents,whicharedifficult,time-consuming,andexpensive

togetandwhichalsoexpireafter17years.Topatent

somethingrequiresthatitbeauniqueandsubstantiallynew

design.Thismadeitimpossibletopatentmostaspectsofthe

IBMPCbecauseitwasdesignedusingpreviouslyexistingparts

thatanybodycouldpurchaseofftheshelf!Infact,mostofthe

importantpartsfortheoriginalPCcamefromIntel,suchasthe

8088processor,8284clockgenerator,8253/54timer,8259

interruptcontroller,8237DMA(directmemoryaccess)

controller,8255peripheralinterface,and8288buscontroller.

ThesechipsmadeuptheheartandsouloftheoriginalPC

motherboard.

BecausethedesignoftheoriginalPCwasnotwholly

patentable,anybodycouldduplicatethehardwareoftheIBM

PC.Allshehadtodowaspurchasethesamechipsfromthe

samemanufacturersandsuppliersIBMusedanddesignanew

motherboardwithasimilarcircuit.Seeminglyasiftoaidinthis,

IBMevenpublishedcompleteschematicdiagramsofits

motherboardsandallitsadaptercardsinverydetailedand

easilyavailabletechnicalreferencemanuals.Ihaveseveralof

theseearlyIBMmanualsandstillrefertothemfromtimeto

timeforspecificcomponent-levelPCdesigninformation.Infact,

Istillrecommendtheseoriginalmanualstoanybodywhowants

todelvedeeplyintoPChardwaredesign.

ThedifficultpartofcopyingtheIBMPCwasthesoftware,which

isprotectedbycopyrightlaw.PhoenixSoftware(todayknown

asPhoenixTechnologies)wasamongthefirsttodevelopalegal



wayaroundthisproblem,whichenabledittofunctionally

duplicate(butnotexactlycopy)softwaresuchastheBIOS.The

BIOSisdefinedasthecoresetofcontrolsoftwarethatdrives

thehardwaredevicesinthesystemdirectly.Thesetypesof

programsarenormallycalleddevicedrivers,soinessence,the

BIOSisacollectionofallthecoredevicedriversusedto

operateandcontrolthesystemhardware.Theoperatingsystem

(suchasDOSorWindows)usesthedriversintheBIOSto

controlandcommunicatewiththevarioushardwareand

peripheralsinthesystem.

SeeChapter5,"BIOS,"p.411.



Phoenix'smethodforlegallyduplicatingtheIBMPCBIOSwas

aningeniousformofreverse-engineering.Ithiredtwoteamsof

softwareengineers,thesecondofwhichhadtobespecially

screenedtoconsistonlyofpeoplewhohadneverbeforeseen

orstudiedtheIBMBIOScode.ThefirstteamdidstudytheIBM

BIOSandwroteascompleteadescriptionofwhatitdidas

possible.Thesecondteamreadthedescriptionwrittenbythe

firstteamandsetouttowritefromscratchanewBIOSthatdid

everythingthefirstteamdescribed.Theendresultwasanew

BIOSwrittenfromscratchwithcodethat,althoughnotidentical

toIBM's,hadexactlythesamefunctionality.

Phoenixcalledthisa"cleanroom"approachtoreverseengineeringsoftware,anditcanescapeanylegalattack.

BecauseIBM'soriginalPCBIOSconsistedofonly8KBofcode

andhadlimitedfunctionality,duplicatingitthroughtheclean

roomapproachwasnotverydifficultnortime-consuming.As

theIBMBIOSevolved,PhoenixaswellastheotherBIOS

companiesfoundthatkeepingupwithanychangesIBMmade

wasrelativelyeasy.Discountingthepoweronselftest(POST)



orBIOSSetupprogram(usedforconfiguringthesystem)

portionoftheBIOS,mostmotherboardBIOSs,eventoday,

haveonlyabout32KB128KBofactivecode.Today,Phoenixand

AmericanMegatrends(AMI)aretheleadingdevelopersofBIOS

softwareforPCsystemandmotherboardmanufacturers.Athird

majorproducerofBIOSsoftware,AwardSoftware,isownedby

PhoenixTechnologies,whichcontinuestosellAwardBIOSbased

products.

AfterthehardwareandBIOSoftheIBMPCwereduplicated,all

thatwasnecessarytoproduceafullyIBM-compatiblesystem

wasDOS.Reverse-engineeringDOS,evenwiththecleanroom

approach,wouldhavebeenadauntingtaskbecauseDOSis

muchlargerthantheBIOSandconsistsofmanymore

programsandfunctions.Also,theoperatingsystemhasevolved

andchangedmoreoftenthantheBIOS,whichbycomparison

hasremainedrelativelyconstant.Thismeansthattheonlyway

togetDOSonanIBMcompatiblewastolicenseit.Thisis

whereMicrosoftcamein.BecauseIBM(whohiredMicrosoftto

writeDOSinthefirstplace)didnotensurethatMicrosoft

signedanexclusivelicenseagreement,Microsoftwasfreeto

sellthesameDOSitdesignedforIBMtoanybodyelsewho

wantedit.WithalicensedcopyofMS-DOS,thelastpiecewas

inplaceandthefloodgateswereopenforIBM-compatible

systemstobeproducedwhetherIBMlikeditornot.

Inretrospect,thisisexactlywhytherearenoclonesor

compatiblesoftheAppleMacintoshsystem.ItisnotthatMac

systemscan'tbeduplicated;infact,Machardwareisfairly

simpleandeasytoproduceusingoff-the-shelfparts.Thereal

problemisthatAppleownstheMacOSaswellastheBIOS,

andbecauseApplehasseenfitnottolicensethem,noother

companycansellanApple-compatiblesystem.Also,notethat

theMacBIOSandOSareverytightlyintegrated;theMacBIOS

isverylargeandcomplex,anditisessentiallyapartoftheOS,

unlikethemuchsimplerandmoreeasilyduplicatedBIOSfound

onPCs.Thegreatercomplexityandintegrationhasallowed



boththeMacBIOSandOStoescapeanyclean-room

duplicationefforts.ThismeansthatwithoutApple'sblessing(in

theformoflicensing),noMacclonesarelikelyevertoexist.

Itmightbeinterestingtonotethatduring19961997,aneffort

wasmadebythemoreliberatedthinkersatAppletolicenseits

BIOS/OScombination,andseveralMac-compatiblemachines

weredeveloped,produced,andsold.CompaniessuchasSony,

PowerComputing,Radius,andevenMotorolainvestedmillions

ofdollarsindevelopingthesesystems,butshortlyafterthese

firstMacclonesweresold,Applecanceledalllicensing!Thiswas

apparentlytheresultofanedictfromSteveJobs,whohadbeen

hiredbacktorunthecompanyandwhowasoneoftheoriginal

architectsoftheclosed-box,proprietary-designMacintosh

systeminthefirstplace.Bycancelingtheselicenses,Apple

virtuallyguaranteedthatitssystemscouldnottrulycompete

alongsideWindows-basedPCs.Alongwithitssmallermarket

sharecomemuchhighersystemcosts,feweravailablesoftware

applications,andfewerhardwareupgradesascomparedtoPCs.

Theproprietarydesignalsomeansthatmajorrepairorupgrade

components,suchasmotherboards,powersupplies,andcases,

areavailableonlyfromAppleatveryhighpricesandupgrades

ofthesecomponentsareusuallynotcosteffective.

Fortunately,Applesrecentlyannouncedtheirintenttoshiftto

Intelx86processors,whichnotonlyindicatesasignificant

performanceimprovementisintheoffingforfutureMac

systems,butitshouldalsomakethemmuchmorecompatible

withPCs.ThiscouldbethebestmoveI'veseenfromApplein

years.Infact,IoftenthinkthatifApplehadadifferentview

andhadlicenseditsOSandBIOSearlyon,thisbookmightbe

calledUpgradingandRepairingMacsinstead!



WhoControlsPCHardware?

AlthoughitisclearthatMicrosofthasalwayscontrolledPC



softwarebyvirtueofitscontroloverthePCoperatingsystem,

whataboutthehardware?ItiseasytoseethatIBMcontrolled

thePChardwarestandardupthrough1987.Afterall,IBM

inventedthecorePCmotherboarddesign;theoriginal

expansionbusslotarchitecture(8/16-bitISAbus);serialand

parallelportimplementations;videocarddesignthroughVGA

andXGAstandards;floppyandharddiskinterfaceand

controllerimplementations;powersupplydesigns;keyboard

interfacesanddesigns;mouseinterface;andeventhephysical

shapes(formfactors)ofeverythingfromthemotherboardto

theexpansioncards,powersupplies,andsystemchassis.All

thesepre-1987IBMPC,XT,andATsystemdesignfeaturesare

stillinfluencingmodernsystemstoday.

Buttometherealquestioniswhichcompanyhasbeen

responsibleforcreatingandinventingnewerandmorerecent

PChardwaredesigns,interfaces,andstandards?WhenIask

peoplethatquestion,Inormallyseesomehesitationintheir

responsessomepeoplesayMicrosoft(butitcontrolsthe

software,notthehardware),andsomesayCompaqorDell,or

theynameafewotherbig-namesystemmanufacturers.Onlya

fewsurmisethecorrectanswerIntel.

Icanseewhymanypeopledon'timmediatelyrealizethis;I

mean,howmanypeopleactuallyownanIntel-brandPC?No,

notjustonethatsays"Intelinside"onit(whichrefersonlyto

thesystemhavinganIntelprocessor),butasystemthatwas

designedandbuiltby,orevenpurchasedthrough,Intel.Believe

itornot,IthinkthatmanyifnotmostpeopletodaydohaveIntel

PCs!

Certainlythisdoesnotmeanthatconsumershavepurchased

theirsystemsfromIntelbecauseInteldoesnotsellcomplete

PCstoendusers.Youcan'tcurrentlyorderasystemfromIntel,

norcanyoupurchaseanIntel-brandsystemfromsomebody

else.WhatIamtalkingaboutisthemotherboard.Inmy

opinion,thesinglemostimportantpartinaPCsystemisthe

motherboard,andI'dsaythatwhoevermadeyourmotherboard



wouldbeconsideredthemanufacturerofyoursystem.Even

backwhenIBMwasthemajorsupplierofPCs,itprimarilymade

themotherboardandcontractedouttheothercomponentsof

thesystem(powersupply,diskdrives,andsoon)toothers.

SeeChapter4,"MotherboardsandBuses,"p.215.



Manyofthetop-sellingsystemmanufacturersdodesignand

maketheirownmotherboards.AccordingtoComputerReseller

Newsmagazine,thetopdesktopsystemsmanufacturersforthe

lastseveralyearshaveconsistentlybeennamessuchasHP,

Compaq(nowownedbyHP),andIBM.Thesecompanies,for

themostpart,dodesignandmanufacturetheirown

motherboards,aswellasmanyothersystemcomponents.In

somecases,theyevendesigntheirownchipsandchipset

componentsfortheirownboards.Althoughsalesarehighfor

theseindividualcompanies,alargeroverallsegmentofthe

marketiswhatthoseintheindustrycallthewhite-boxsystems.

White-boxisthetermusedbytheindustrytorefertowhat

wouldotherwisebecalledgenericPCsthatis,PCsassembled

fromacollectionofindustry-standard,commerciallyavailable

components.Thewhite-boxdesignationcomesfromthefact

thathistoricallymostofthechassisusedbythistypeofsystem

havebeenwhite(orivoryorbeige).

Thegreatthingaboutwhite-boxsystemsisthattheyuse

industry-standardcomponentsthatareinterchangeable.This

interchangeabilityisthekeytofutureupgradesandrepairs

becauseitensuresthataplethoraofreplacementpartswillbe

availabletochoosefromandwillinterchange.Formanyyears,I

haverecommendedavoidingproprietarysystemsand

recommendedmoreindustry-standardwhite-boxsystems

instead.



Companiessellingwhite-boxsystemsdonotreallymanufacture

thesystems;theyassemblethem.Thatis,theypurchase

commerciallyavailablemotherboards,cases,powersupplies,

diskdrives,peripherals,andsoon,andassembleandmarket

everythingtogetherascompletesystems.Dell,Gateway,and

Micron(nowMPC)aresomeofthelargerwhite-boxsystem

assemblerstoday,buthundredsmorecouldbelisted.Inoverall

totalvolume,thisendsupbeingthelargestsegmentofthePC

marketplacetoday.Whatisinterestingaboutwhite-boxsystems

isthat,withveryfewexceptions,youandIcanpurchasethe

samemotherboardsandothercomponentsanyofthewhiteboxmanufacturerscan(althoughwewouldprobablypaymore

thantheydobecauseofthevolumediscountstheyreceive).We

canassembleavirtuallyidenticalwhite-boxsystemfrom

scratchourselves,butthatisastoryforChapter20,"Building

orUpgradingSystems."

Notethatsomeofthesewhite-boxcompanieshaveincredible

salesforexample,DellhastakenthetopPCsalesspotfrom

Compaq(nowHP),whohadhelditformanyyears.Gateway

andtheotherwhite-boxsystembuildersarenotfarbehind.

Thepointofallthisis,ofcourse,thatifDell,Gateway,MPC,

andothersdonotmanufacturetheirownmotherboards,who

does?YouguesseditIntel.Notonlydothosespecificcompanies

mainlyuseIntelmotherboards,ifyoucheckaround,you'llfind

todaythatmanyofthesystemsinthewhite-boxmarketcome

withIntelmotherboards.TheonlyplaceInteldoesn'thavea

presenceistheAMD-basedsystemsdesignedtosupport

Athlon-brandedprocessors.

Althoughthisisanextremecase,onereviewof10systemsin

ComputerShoppermagazinelisted8outofthe10systems

evaluatedashavingIntelmotherboards.Infact,those8used

theexactsameIntelmotherboard.Therefore,thosesystems

differedonlyinthecosmeticsoftheexteriorcaseassemblies

andbywhichperipheralcomponents,suchasvideocard,disk

drives,keyboard,andsoon,wereselected.Thefunnything



wasthatmanyoftheperipheralitemswereidenticalamongthe

systemsaswell.Beforeyoucomparepreassembledsystems

fromdifferentmanufacturers,besuretogetalistingofwhich

partstheyareusing;youmightbesurprisedtoseehowsimilar

thesystemsonthemarketatanygiventimecanbe.

AlthoughIntelstilldominatesmotherboardsales,that

dominancehasfalteredsomewhatfromafewyearsback.

BecauseofIntel'sfocusonRambusmemoryduringtheearly

Pentium4days,manyofthelower-costsystembuilders

switchedtoalternativeproducts.Also,mostofIntel'sboards

aredesignedtomakeoverclockingextremelydifficult,so

"hotrod"systembuildersoftenchoosenon-Intelboardsthatuse

AMDprocessors.

AMD,ontheotherhand,manufacturesprocessorsandchipsets

butnotcompletemotherboards.Forthat,AMDreliesona

numberofothermotherboardmanufacturerstomakeboards

designedtoacceptAMDprocessors.Theseboardsuseeither

theAMDchipsetsorotherchipsetsmadebythird-party

companiesspecificallytosupportAMDprocessors.Thesame

motherboardcompaniesmakingboardsforAMD

processorbasedsystemsalsomakemotherboardsforIntel

processorbasedsystems,inessencecompetingdirectlywith

Intel'sownmotherboards.

See"Chipsets,"p.253.



HowdidIntelcometodominatetheinteriorofourPCs?Intel

hasbeenthedominantPCprocessorsuppliersinceIBMchose

theIntel8088CPUintheoriginalIBMPCin1981.By

controllingtheprocessor,Intelnaturallycontrolledthechips

necessarytointegrateitsprocessorsintosystemdesigns.This

naturallyledIntelintothechipsetbusiness.Itstartedits



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