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Chapter 11.  Graphics and Sound

Chapter 11.  Graphics and Sound

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VideoDisplaySystem

Thevideosubsystemofamodernlaptop/notebooksystem

consistsoftwomaincomponents:

VideodisplayAflat-paneldisplayasfoundonlaptop

computers.

Graphicsprocessor(alsocalledthevideochipor

graphicschip)Builtintothemotherboardinvirtuallyevery

laptopcomputer.Somelaptopsintegratethegraphicsas

partofthemotherboardchipset,butsomemodelsusea

discretegraphicsprocessorwithitsownvideomemory.

Thissectionexaminesthedisplayandadaptertechnologies

usedinportablesystems.



MajorLaptopDisplayFeaturestoConsider

Unlikedesktopcomputers,whichallowyoutoreplacethevideo

cardandthedisplayfreely,laptopcomputershavebuilt-in

graphicsanddisplaycomponents.Becauseupgradeoptionsare

muchmorelimitedinalaptopthaninadesktop,it'sessential

tochoosealaptop,inpart,basedonitsdisplayqualityand

displayfeatures.Theessentialfeaturestoconsiderinalaptop's

displaysystemincludethefollowing:

Flat-paneldisplaytype

Screenresolutionandsize

Pixelsperinch(ppi)



Brightnessandcontrast

Responsetime

Manufacturerpolicyconcerning"dead"pixels

Externaldisplayinterfaces

Thegraphicsprocessorormotherboardchipsetused

Videomemorysizeandtype

Memorysizeadjustmentoptions

Multiplemonitorsupport(DualView)

CardBus/PCCard/ExpressCardsupport

3Dgraphicssupport

TVinput/outputsupport

Driversupport

Thesetopicsarecoveredinthefollowingsubsections.



EarlyPortableDisplays:CRTandPlasma

Adisplaycanuseoneofseveraltechnologies.Theoriginal

displaytechnologyusedinoldersuitcase-sizedportablessuch

astheoriginalCompaqPCsandtheIBMPortablePCiscathoderaytube(CRT)technology.CRTsconsistofavacuumtube

enclosedinglass.Oneendofthetubecontainsanelectrongun



assemblythatprojectsthreeelectronbeams,oneeachforthe

red,green,andbluephosphorsusedtocreatethecolorsyou

seeonscreen.Theotherendcontainsascreenwitha

phosphorouscoating.

Whenheated,theelectrongunemitsastreamofhigh-speed

electronsthatareattractedtotheotherendofthetube.Along

theway,afocuscontrolanddeflectioncoilsteerthebeamtoa

specificpointonthephosphorousscreen.Whenstruckbythe

beam,thephosphorglows.Thislightiswhatyouseewhenyou

watchTVorlookatyourcomputerscreen.Threelayersof

phosphorsareused:red,green,andblue.Ametalplatecalled

ashadowmaskisusedtoaligntheelectronbeams;ithasslots

orholesthatdividethered,green,andbluephosphorsinto

groupsofthree(oneofeachcolor).Varioustypesofshadow

masksaffectpicturequality,andthedistancebetweeneach

groupofthree(thedotpitch)affectspicturesharpness.

CRTsarewaytoobigandheavyforportableuse.Assoonas

alternativetechnologieswereavailableforportablesystems,

theoldbulkyCRTsbecameathingofthepast.Someportables

experimentedwithtechnologiessuchasgas-plasma(oftenjust

calledplasma)andelectroluminescent(EL)displays,butthey

werenormallymonochromesolutionsthatwereconfinedtoonly

afewselectmodels.Mostportablesinthelate1980sandearly

1990sbeganusingliquidcrystaldisplay(LCD)technology.

Virtuallyalldisplayscreensinportablesystemssincethemid90shaveusedcolorLCDtechnology.



Note

Gas-plasmadisplaytechnologywasusedinafew

portablesfromthelate1980s.Plasmadisplays

provideaCRT-qualitypictureonathin,flatscreen

usingtwoglasspanesfilledwithaneon/xenongas

mixture.Someweremonochrome(usuallyorange),

whereasotherswerefullcolor.Manyoftheearly386



and486portablesusedgas-plasmadisplays.

Unfortunately,theseplasmadisplayswereheavy

andrequiredfarmorepowerthanLCDs,meaning

thatthesystemsusingplasmadisplayswereAC

poweredonly;theycouldnotrunonbatteries.As

such,plasmadisplaysneverbecameapractical

alternativefortheportablecomputermarket.



LiquidCrystalDisplays(LCDs)

AnLCDconsistsoftwosheetsofaflexible,polarizingmaterial

withalayerofliquidcrystalsolutionbetweenthem.Ifyoupress

gentlyonanLCDscreenwhileitislit,youcanseehowitgives

slightly,displacingtheliquidinside.Whenanelectriccurrentis

passedthroughtheliquid,thecrystalsalignandbecome

semipermeabletolight.

LCDshavelow-glare,completelyflatscreensandlowpower

requirements(5wattsversusnearly100wattsforanordinary

monitor).Thecolorqualityofanactive-matrixLCDpanel

actuallyexceedsthatofmostCRTdisplays.

Asidefromtheirlightweight,LCDsofferanumberofadditional

benefitswhencomparedtoconventionalCRT"glasstube"

monitors:

Largereffectiveviewablearea

Noimagedistortion

Lowerpowerrequirementsandlessheatgenerated



Noelectromagneticemissions

A15"LCDisessentiallyequalinusabilitytoa17"orlargerCRT,

andsomelaptopcomputersnowoffer17"screens.Thisisdue

notonlytotheresolutionsavailablebutalsotothefactthatyou

generallysitclosertoalaptop/notebookdisplay,thusmakinga

smallerdisplaymoreusable.

BecauseLCDsusedirectaddressingofthedisplay(eachpixelin

thepicturecorrespondswithatransistor),theyproduceahighprecisionimage.LCDsdon'thavethecommonCRTdisplay

problemsofpin-cushiondistortion,barreldistortion,or

convergenceerrors(halosaroundtheedgesofonscreen

objects).

LCDsareidealforportablesbecausetheyuselesspower(5

wattsversusnearly100wattsforadesktopCRT)andgenerate

lessheatthanotherdisplaytechnologies.Theyarealso

intrinsicallysafe;withLCDstherearenoconcernsover

electromagneticverylowfrequency(VLF)orextremelylow

frequency(ELF)emissions.



HowLCDsWork

InanLCD,apolarizingfiltercreatestwoseparatelightwaves.

Thepolarizingfilterallowslightwavesthatarealignedonlywith

thefiltertopassthrough.Afterpassingthroughthepolarizing

filter,theremaininglightwavesareallalignedinthesame

direction.Whenasecondpolarizingfilterisalignedataright

angletothefirst,allthosewavesareblocked.Whentheangle

ofthesecondpolarizingfilterischanged,theamountoflight

allowedtopasscanbechanged.Itistheroleoftheliquid

crystalcelltochangetheangleofpolarizationandcontrolthe

amountoflightthatpassesthrough.Theliquidcrystalsarerodshapedmoleculesthatflowlikealiquid.Theyenablelightto



passstraightthrough,butanelectricalchargealterstheir

orientationandtheorientationofthelightpassingthrough

them.AlthoughmonochromeLCDsdonothavecolorfilters,

theycanhavemultiplecellsperpixelforcontrollingshadesof

gray.

InacolorLCD,anadditionalfilterhasthreecellsforeach

pixeloneeachfordisplayingred,green,andbluewitha

correspondingtransistorforeachcell.Thered,green,andblue

cells,whichmakeupapixel,aresometimesreferredtoas

subpixels.Theabilitytocontroleachcellindividuallyhas

enabledMicrosofttodevelopanewmethodofimprovingLCD

textquality.BeginningwithWindowsXP,youcanenablea

featurecalledClearTypethroughtheDisplayPropertiesdialog

box.



LCDTypes

TwobasicLCDchoicesareavailabletodayonnotebook

computers:active-matrixanalogcolorandactive-matrixdigital.

MonochromeLCDdisplaysareobsoleteforPCs,althoughthey

remainpopularforsimpleorganizerdevicesandaresometimes

usedforindustrialdisplaypanels.Passive-matrixdisplaysusing

dual-scantechnologywerepopularforlow-costnotebook

modelsuntilafewyearsago.Currently,alllow-costnotebooks

soldusethebrighteranalogordigitalactive-matrixdesigns

originallyfoundonmoreexpensivenotebookcomputers.

Passive-matrixdisplaysarestillusedwithhandheldorganizers

orforindustrial-usedesktopdisplaypanelsbecauseoftheir

relativelylowcostandenhanceddurabilitycomparedtoactivematrixmodels.



Note

Themostcommonpassive-matrixdisplaysuseda

supertwistnematicdesign,sothesepanelswere



oftenreferredtoasSTNs.Active-matrixpanels

usuallyuseathin-filmtransistordesignandare

thereforereferredtoasTFTs.



Dual-Scan(Passive-Matrix)Displays

Thedual-scandisplay,sometimescalledapassive-matrix

display,hasanarrayoftransistorsrunningdownthex-andyaxesoftwosidesofthescreen.Thenumberoftransistors

determinesthescreen'sresolution.Forexample,adual-scan

displaywith800transistorsalongthex-axisand600alongthe

y-axiscreatesagridsimilartothehorizontalandverticallines

onapieceofgraphpaper.Eachpixelonthescreeniscontrolled

bythetwotransistorsrepresentingitscoordinatesonthexandy-axes.

Ifatransistorinadual-scandisplayshouldfail,awholelineof

pixelsisdisabled,causingablacklineacrossthescreen(either

horizontallyorvertically).Thereisnosolutionforthisproblem

otherthantoreplacethedisplayorjustlivewithit.Theterm

dualscancomesfromthefactthatthescreenisdividedinhalf,

witheachhalfbeingrefreshedsimultaneously.

Dual-scandisplaysaregenerallyinferiortoactive-matrix

screens.Dual-scandisplaystendtobedimmerbecausethe

pixelscannotberefreshedasoftenasthoseonanactive-matrix

display.Dual-scanpanelsalsoarepronetoghostimagesand

aredifficulttoviewfromanangle,makingithardfortwoor

morepeopletoviewthesamescreen.

However,newerpassive-matrixtechnologies,suchascolor

super-twistnematic(CSTN),double-layersuper-twistnematic

(DSTN),andespeciallyhigh-performanceaddressing(HPA)



screens,haveimprovedtheappearanceofpassive-matrix

screens.Althoughthesenewerdisplaysofferbetterresponse

ratesandcontrastproblemsthatplaguedmanyoftheearlier

displaytypestheyarestillnotassharporasfastasanactivematrixscreenandhavebeenreplacedbyactive-matrixdisplays

inallpricelevelstoday.

Foreverydayuse,thedrawbacksofapassive-matrixdisplayare

mostnoticeableduringvideo-intensiveapplications,suchas

presentations,full-colorgraphics,video,andfast-moving

games,orunderbrightlightingconditions,suchasinawindow

seatonanairplane,outdoors,orinofficeswithalotofwindow

lighting.Forindoorcomputingtaskssuchaswordprocessing

andemail,whichconsistlargelyofreadingwordsonscreen,the

passive-matrixdisplayisquiteserviceable,evenforlong

periodsoftime.

Thestandardsizefordual-scandisplaysrangedfrom10.4

inches(measureddiagonally)at640x480,upto12.1-inchor

13.3-inchdisplaysat800x600or1024x768resolution.Dualscandisplaysareobsoleteinmodernsystems,thanksto

improvementsintheyieldandreductionsinthepriceofactivematrixLCDscreens.



Active-MatrixDisplays

Anactive-matrixdisplaydiffersfromadual-scandisplayinthat

itcontainsthreetransistorsforeverypixelonscreen(color

displays)ratherthanjustattheedges.Thetransistorsare

arrangedonagridofconductivematerial,witheachconnected

toahorizontalandaverticalmember.Selectedvoltagesare

appliedbyelectrodesattheperimeterofthegridtoaddress

eachpixelindividually.Thus,anactive-matrixscreenis

comparabletoasheetofgraphpaperthathasadot

(representingatransistor)ateachintersectionofhorizontaland

verticallines.



Mostactive-matrixdisplaysuseathin-filmtransistor(TFT)

array.TFTisamethodforpackagingfromone(monochrome)

tothree(RGBcolor)transistorsperpixelwithinaflexible

materialthatisthesamesizeandshapeasthedisplay.

Therefore,thetransistorsforeachpixelliedirectlybehindthe

liquidcrystalcellstheycontrol.

TwoTFTmanufacturingprocessesaccountformostofthe

active-matrixdisplaysonthemarkettoday:hydrogenated

amorphoussilicon(a-Si)andlow-temperaturepolysilicon(p-Si).

Theseprocessesdifferprimarilyintheircosts.Atfirst,mostTFT

displaysweremanufacturedusingthea-Siprocessbecauseit

requiredlowertemperatures(lessthan400°C)thanthep-Si

processofthetime.Now,lower-temperaturep-Si

manufacturingprocessesaremakingthismethodan

economicallyviablealternativetoa-Si.

ToimprovehorizontalviewinganglesinthelatestLCDdisplays,

somevendorshavemodifiedtheclassicTFTdesign.For

example,Hitachi'sin-planeswitching(IPS)designalsoknownas

STFTalignstheindividualcellsoftheLCDparalleltotheglass,

runningtheelectriccurrentthroughthesidesofthecellsand

spinningthepixelstoprovidemoreevendistributionofthe

imagetotheentirepanelarea.Fujitsu'ssimilarmultidomain

verticalalignment(MVA)technologyisusedinmanyrecent

notebookdisplays.MVAdividesthescreenintodifferentregions

andchangestheangleoftheregionstoprovideawiderviewing

anglethantraditionalTFTdisplays.

AlthoughaTFTdisplayhasagreatmanytransistors4,410,000

foracolor1400x1050displayeachpixeldoesnothaveitsown

separatesignalconnection.Instead,voltagesareapplied

throughconnectionsforeachrowandcolumn,muchlikethe

transistorsinapassive-matrixdisplay.

Becauseeverypixelisindividuallycontrolledbyitsown

transistorcircuit,itcanberefreshedatveryhighrates,creating

adisplaythatismorevividthanadual-scanpanel.Theviewing



angleisalsogreater,enablingmultipleviewerstogatheraround

thescreen,andrefreshesarefasterandcrisper,withoutthe

fuzzinessofthedualscans,eveninthecaseofgamesorfullmotionvideo.

Mostlaptop/notebooksystemstodayusescreensfrom14.1

inches(diagonal)through17inches,withsomehigh-end

modelsusingwide-screendisplaysupto17inches.Most

systemsfeaturinga14.1-inchscreenrunXGAresolution

(1024x768),whereashigh-endsystemsincludescreensupto

1600x1200resolutionormore.Higherresolutionsandsizesare

possible,butIquestionwhetheranythinglargerthana17-inch

displayisworkableforaportablesystem.Inaddition,

increasingtheresolutionwithoutincreasingthesizemakestext

andiconsdifficulttosee.Manyportablesystemsnowalso

includeAGPbusvideoadapterswithupto128MBofvideoRAM,

providingextraspeedandcapability.AgoodTFTdisplayand

integratedAGPorPCIExpressadapterrivalthequalityand

performanceofaqualitymonitorandvideoadapterina

desktopsystem.Infact,a15-inchTFTdisplay(which,unlike

mostconventionalmonitors,describestheactualdiagonalsize

oftheimage)generallyhaspicturequalityandusabilityequal

toa17-inchCRTdisplay.



Resolution

Resolutionistheamountofdetailamonitorcanrender.This

quantityisexpressedinthenumberofhorizontalandvertical

pictureelements,orpixels,containedinthescreen.Thegreater

thenumberofpixels,themoredetailedtheimages.The

resolutionrequireddependsontheapplication.Character-based

applications(suchasDOScommand-lineprograms)require

verylowresolutions,whereasgraphics-intensiveapplications

(suchasdesktoppublishingandWindowssoftware)requirea

greatdealmore.WithWindows,themoreresolutionyouhave,

thegreaterthesizeofyourdesktop,whichmeansyoucanhave



moreprogramsorwindowsopenatonce,withoutoverlapping.

It'simportanttorealizethatCRTsaredesignedtohandlea

rangeofresolutionsnatively,butflat-paneldisplays(both

desktopandnotebook)arebuilttorunasinglenative

resolutionandmustscaletootherchoices.OlderLCDpanels

handledscalingpoorly,buteventhoughcurrentTFTdisplays

performscalingbetter,thebestresultswithvariousresolutions

arestillfoundwithCRTs.

AsPCvideotechnologydeveloped,thescreenresolutionsthat

videoadapterssupportedgrewatasteadypace.Table11.1

liststhestandardresolutionsusedinlaptopgraphicsadapters

anddisplays(includingexternalmonitors),andtheterms

commonlyusedtodescribethem.

Table11.1.LaptopGraphicsDisplayResolution

Standards

Display

Standard



LinearPixels

(HxV)



TotalPixels



AspectRatio



VGA



640x480



307,200



1.33



SVGA



800x600



480,000



1.33



XGA



1024x768



786,432



1.33



WXGA+



1440x900



1,296,000



1.60



SXGA



1280x1024



1,310,720



1.25



SXGA+



1400x1050



1,470,000



1.33



WSXGA



1600x1024



1,638,400



1.56



WSXGA+



1680x1050



1,764,000



1.60



UXGA



1600x1200



1,920,000



1.33



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