CMPU224– ComputerOrganizationJasonWaterman

CourseOverview

Today

• Coursetheme• Courselogistics• Fourrealities

2/16/21 CMPU224-- ComputerOrganization 2

Whatisthiscourseabout?

• UnderstandingComputerSystems• Thehardwareandsystemsoftwarethatworktogethertorunapplicationprograms

Mainmemory

I/O bridgeBus interface

ALU

Register fileCPU

System bus Memory bus

Disk controller

Graphicsadapter

USBcontroller

MouseKeyboard DisplayDisk

I/O bus

executable stored on disk

PC

Expansionslotsforotherdevicessuchasnetworkadapters

2/16/21 CMPU224-- ComputerOrganization 3

Whatahappenswhenaprogramruns?• Arunningprogramexecutesinstructions• Theprocessorfetchesaninstructionfrommemory• Decode:Figureoutwhichinstructionthisis• Execute:i.e.,addtwonumbers,accessmemory,checkacondition,jumptofunction,andsoforth• Theprocessormovesontothenextinstructionandsoon

Mainmemory

I/O bridgeBus interface

ALU

Register fileCPU

System bus Memory bus

Disk controller

Graphicsadapter

USBcontroller

Mouse Keyboard DisplayDisk

I/O bus

executable stored on disk

PC

Expansionslotsforotherdevicessuchasnetworkadapters

2/16/21 CMPU334-- OperatingSystems 4

2/16/21 CMPU224-- ComputerOrganization 5

Whatiscomputerorganization?

2/16/21 CMPU224-- ComputerOrganization 6

Application

Physics

Whatiscomputerorganization?

2/16/21 CMPU224-- ComputerOrganization 7

Application

Physics

Gaptoolargetobridgeinonestep

Whatiscomputerorganization?

2/16/21 CMPU224-- ComputerOrganization 8

Application

Physics

Gaptoolargetobridgeinonestep

Initsbroadestdefinition,computerorganizationisthedesignoftheabstraction/implementationlayersthatallowustoexecuteinformationprocessing applicationsefficientlyusingmanufacturingtechnologies.

Whatiscomputerorganization?

2/16/21 CMPU224-- ComputerOrganization 9

ApplicationAlgorithm

ProgrammingLanguageOperatingSystem

InstructionSetArchitectureMicroarchitecture

Register-TransferLevelGatesCircuitsDevicesPhysics

Whatiscomputerorganization?

2/16/21 CMPU224-- ComputerOrganization 10

ApplicationAlgorithm

ProgrammingLanguageOperatingSystem

InstructionSetArchitectureMicroarchitecture

Register-TransferLevelGatesCircuitsDevicesPhysics

CMPU-224ComputerOrganization

CourseTheme:AbstractionIsGoodButDon’tForgetReality• MostCScoursesemphasizeabstraction• Abstractdatatypes• Asymptoticanalysis

• Theseabstractionshavelimits• Especiallyinthepresenceofbugs• Needtounderstanddetailsofunderlyingimplementations

• Usefuloutcomesfromtaking224• Becomemoreeffectivesoftwaredevelopers

• Abletofindandeliminatebugsefficiently• Abletounderstandandtuneforprogramperformance

• Prepareforlater“systems”classesinCS• Compilers,OperatingSystems,Networks,ComputerArchitecture,ParallelProgramming

2/16/21 CMPU224-- ComputerOrganization 11

Today

• Coursetheme• Courselogistics• Fourrealities

2/16/21 CMPU224-- ComputerOrganization 12

WebsiteandTextbooks

• https://cs224.cs.vassar.edu• Completescheduleoflectures,exams,andassignments

• RandalE.BryantandDavidR.O’Hallaron (Required)• ComputerSystems:AProgrammer’sPerspective,ThirdEdition2016• http://csapp.cs.cmu.edu• Thisbookreallymattersforthecourse!

• Howtosolveassignments• Practiceproblemstypicalofexamproblems

• BrianKernighanandDennisRitchie(Optional)• TheCProgrammingLanguage,SecondEdition1988• StillthebestbookaboutC,fromtheoriginatorsofthelanguage

2/16/21 CMPU224-- ComputerOrganization 13

CourseComponents

• Lectures• Higherlevelconcepts

• Assignments• Theheartofthecourse• 1-2weekseach• Providein-depthunderstandingofthematerial

• Exams(midterm+final)• Testyourunderstandingofconcepts&mathematicalprinciples

• Prerequisites(talktomeifyouhaven’tcompletedtheseclasses)• CMPU102

2/16/21 CMPU224-- ComputerOrganization 14

YourProfessor

• OfficeHours:• TuesdayandThursday3pm-5pm• VirtualOffice:Zoom• Ihaveanopendoorpolicy

• Ifmydoorisopen,feelfreetocomeinandtalktome

• Officehoursbyappointmentaswell–messagemeonslack

• Background• Research

2/16/21 CMPU224-- ComputerOrganization 15

Grading

• 30%Midterm• 40%Assignments• 30%Final

2/16/21 CMPU224-- ComputerOrganization 16

Attendance

• Ireallywanttoseeyouineachaneveryclassinpersonorremotely• We’llworkonproblemstogetherduringclassandlabs• I’llleavetimeforquestions

• OurclassesatVassararesmall• Comingtoclassisoneofthebestwaystolearnthematerial

2/16/21 CMPU224-- ComputerOrganization 17

ElectronicDevicesinClass

• Pleaseturnoffyourphoneorputin“donotdisturb”mode• It’sdistractingtoyouandyourclassmates• Ifyouwouldliketouseyourlaptopfortakingnotes• Youarewelcometodoso,butpleaseonlyuseitfornotes

• Theuseofelectronicdevicesfornon-classrelatedpurposesisstronglydiscouraged• Considerthisclasstobeanoasisfromyourdevice

2/16/21 CMPU224-- ComputerOrganization 18

CEQ’s• Givesmefeedbackabouthowthecourseisgoing• Awayforyouto“grade”thecourse

• Usedbythedepartmentandadministration• Mygoalistoearn“5s”fromeachandeveryoneofyou• IfIamnotlivinguptothoseexpectations,pleasecometalktomeASAP• Pleasedon’twaittilltheendofthecourse

• Helpmemakethecoursebetterforyouandyourclassmates

• IwillkeepworkinguntilIcanmeetthosegoals

2/16/21 CMPU224-- ComputerOrganization 19

StudentTeacherEngagedPedagogicalPartnership(STEPP)

• Pedagogicalpartnershipprogram• Semester-longfaculty-studentcollaboration• ANon-CSstudentobserverwillsitinandobserve• Opportunityformetoreceiveconstructivefeedbackonthecourse• Collaborativewithastudentpartnertoaddressteachinggoals

• Howyoucanhelp• ReachouttoMarkandshareyourfeedbackabouthowtheclassisgoing

MarkFossescaSecond-yearENSTmajor

2/16/21 CMPU224-- ComputerOrganization 20

• Allassignmentsareduebythedeadlinestatedontheassignmenthandout• Allstudentswillreceiveabudgetof5slipdaysforthecourse• Nomorethan2slipdayscanbeusedonanyassignment• Ifyouuseaslipdaythenewduedatewillbe24hoursfromtheoriginaldate• Slipdayscanonlyusedonassignment,notonthemidtermorfinals

SlipDays

2/16/21 CMPU224-- ComputerOrganization 21

• Ihopeeveryoneinthisclasswillremainhappyandhealthy• Ifyouhaveaseriouspersonalissue,talktoyouracademicadvisorassoonaspossible• Theyareequippedtocoordinateplansforgettingyoubackontrackinthisclassaswellasyourotherclasses• Iwillcooperatewithsuchplans,butIcannotconstructthemindependentlyoftheacademicadvisors

SeriousPersistentPersonalIssues

2/16/21 CMPU224-- ComputerOrganization 22

• Ifyouneedacademicaccommodations,pleasegetthehelpyouneed

• AcademicaccommodationsareavailableforstudentsregisteredwiththeOfficeofAccessibilityandEducationalOpportunity(AEO)

• Studentswhoneedaccommodationsshouldmeetwithmeearlyinthesemestertodiscusstheaccommodations

AcademicAccommodations

2/16/21 CMPU224-- ComputerOrganization 23

• Examsandassignmentsmustbethesoleworkofthestudentturningitin• Whatischeating?• Sharingcodeorotherelectronicfiles:eitherbycopying,retyping,lookingat,orsupplyingacopyofafilefromthisoraprevioussemester• Sharingwrittenassignmentsorexams:lookingat,copying,orsupplyinganassignmentorexam• Usingother’scodefromthisorpreviousofferingsof224orfromanyothersourcesuchascodefoundontheInternet

• UsingcodefromthetextbookorfromtheclasswebsiteisalwaysOK

AcademicIntegrity

2/16/21 CMPU224-- ComputerOrganization 24

LearningEnvironment

• Iamcommittedtoprovidingasafelearningenvironmentforallstudents

• Freefromallformsdiscriminationandsexualharassment

• Ifyouhaveexperiencedanyoftheseincidents• Youarenotalone• VassarCollegehasstaffmemberstrainedtosupportyou

2/16/21 CMPU224-- ComputerOrganization 25

Today

• Coursetheme• Courselogistics• Fourrealities

2/16/21 CMPU224-- ComputerOrganization 26

GreatReality#1:Ints arenotIntegers,FloatsarenotReals

• Example:isx2 ≥0?• Float’s:Yes!

• Int’s:• 40000*40000=1600000000• 50000*50000=??

2/16/21 CMPU224-- ComputerOrganization 27

Source:xkcd.com/571

GreatReality#2:You’veGottoKnowAssemblyandC

• Chancesare,you’llneverwriteprogramsinassembly• Compilersarebetterandmorepatientthanyouare

• But:Understandingassemblyiskeytomachine-levelexecutionmodel• Behaviorofprogramsinpresenceofbugs

• High-levellanguagemodelsbreakdown• Tuningprogramperformance

• Understandoptimizationsdone/notdonebythecompiler• Understandingsourcesofprograminefficiency

• Implementingsystemsoftware• Compilerhasmachinecodeastarget• Operatingsystemsmustmanageprocessstate

• Creating/fightingmalware• x86assemblyisthelanguageofchoice

2/16/21 CMPU224-- ComputerOrganization 28

GreatReality#3:MemoryMattersRandomAccessMemoryIsanUnphysicalAbstraction

• Memoryisnotunbounded• Itmustbeallocatedandmanaged• Manyapplicationsarememorydominated

• Memoryperformanceisnotuniform• Cacheeffectscangreatlyaffectprogramperformance• Adaptingprogramtocharacteristicsofmemorysystemcanleadtomajorspeedimprovements

2/16/21 CMPU224-- ComputerOrganization 29

CachesMatter

Mainmemory

I/ObridgeBusinterface

ALU

Registerfile

CPUchip

Systembus Memorybus

Cachememories

2/16/21 CMPU224-- ComputerOrganization 30

MemorySystemPerformanceExample

• Hierarchicalmemoryorganization• Performancedependsonaccesspatterns• Includinghowstepthroughmulti-dimensionalarray

2/16/21 CMPU224-- ComputerOrganization 31

void copyji(int src[2048][2048],int dst[2048][2048])

{int i,j;for (j = 0; j < 2048; j++)

for (i = 0; i < 2048; i++)dst[i][j] = src[i][j];

}

void copyij(int src[2048][2048],int dst[2048][2048])

{int i,j;for (i = 0; i < 2048; i++)

for (j = 0; j < 2048; j++)dst[i][j] = src[i][j];

}

81.8ms4.3ms 2.0GHzIntelCorei7Haswell

GreatReality#4:There’smoretoperformancethanasymptoticcomplexity• Constantfactorsmattertoo• Andevenexactoperationcountdoesnotpredictperformance• Easilysee10:1performancerangedependingonhowcodewritten• Mustoptimizeatmultiplelevels:algorithm,datarepresentations,procedures,andloops

• Mustunderstandsystemtooptimizeperformance• Howprogramscompiledandexecuted• Howtomeasureprogramperformanceandidentifybottlenecks• Howtoimproveperformancewithoutdestroyingcodemodularityandgenerality

2/16/21 CMPU224-- ComputerOrganization 32

WelcomeandEnjoy!

2/16/21 CMPU224-- ComputerOrganization 33