L09 Hardware and State - inst.eecs.berkeley.edu

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CS61C:GreatIdeasinComputerArchitecture

IntroductiontoHardware:RepresentationsandState

Instructors:Krste Asanović andRandyH.Katz

http://inst.eecs.Berkeley.edu/~cs61c/fa17

1Fall2017 -- Lecture#99/21/17

FromLastTime:WhereAreWeNow?

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Translation:CompilationtoAssembly1. Replacepseudowithrealinstructions2. Resolvelocaljumps,branches3. CreateSymbol,RelocationTables

SymbolTable:LabelsdefinedorreferencedRelocationTable:Addresslocationstobeadjusted

3.2. CALLING CONVENTION 29

Figure 3.1: Steps of translation from C source code to a running program. These are the logical steps,although some steps are combined to accelerate translation. We use the Unix file suffix name convention for

each type of file. The equivalent suffixes in MS-DOS are .C, .ASM, .OBJ, .LIB, and .EXE.

.o file 1text 1data 1info 1

.o file 2text 2data 2info 2

Linker

a.outRelocated text 1Relocated text 2Relocated data 1Relocated data 2

Linker(2/3)

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FourTypesofAddresses

• PC-RelativeAddressing(beq,bne,jal; lla: auipc/addi)– Neverneedtorelocate(PIC:positionindependentcode)

• AbsoluteFunctionAddress(la:auipc/lw + jalr)– Alwaysrelocate

• ExternalFunctionReference(la:auipc/lw + jalr)– Alwaysrelocate

• StaticDataReferences(lui/addi)– Alwaysrelocate

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ResolvingReferences(1/2)

• Linkerassumesfirstwordoffirsttextsegmentisataddress0x10000 forRV32.– (Morelaterwhenwestudy“virtualmemory”)

• Linkerknows:– Lengthofeachtextanddatasegment– Orderingoftextanddatasegments

• Linkercalculates:– Absoluteaddressofeachlabeltobejumpedto(internalorexternal)andeachpieceofdatabeingreferenced

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ResolvingReferences(2/2)

• Toresolvereferences:– Searchforreference(dataorlabel)inall“user”symboltables– Ifnotfound,searchlibraryfiles(e.g.,forprintf)– Onceabsoluteaddressisdetermined,fillinthemachinecodeappropriately

• Outputoflinker:executablefilecontainingtextanddata(plusheader)

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WhereAreWeNow?

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LoaderBasics

• Input:ExecutableCode(e.g.,a.out forRISC-V)• Output:(programisrun)• Executablefilesarestoredondisk• Whenoneisrun,loaderloadsitintomemoryandstartit• Inreality,loaderistheoperatingsystem(OS)– LoadingisoneoftheOStasks

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Loader…WhatDoesItDo?

• Readsexecutablefile’sheadertodeterminesizeoftextanddatasegments• Createsnewaddressspaceforprogramlargeenoughtoholdtextanddatasegments,alongwithastacksegment

• Copiesinstructions+datafromexecutablefileintothenewaddressspace• Copiesargumentspassedtotheprogramontothestack• Initializesmachineregisters

– Mostregisterscleared,butstackpointerassignedaddressof1stfreestacklocation• Jumpstostart-uproutinethatcopiesprogram’sargumentsfromstacktoregisters&setsthePC– Ifmainroutinereturns,start-uproutineterminatesprogramwiththeexitsystemcall

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PeerInstructionAtwhatpointinprocessareallthemachinecodebitsdeterminedforthefollowingassemblyinstructions:1)add x6, x7, x82)jal x1, fprintf

A:1)&2)AftercompilationB:1)Aftercompilation,2)AfterassemblyC:1)Afterassembly,2)Afterlinking:1)Afterassembly,2)Afterloading

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ExampleCProgram:Hello.c

#include <stdio.h> int main() { printf("Hello, %s\n", "world"); return 0;

}

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CompiledHello.c:Hello.s.text.align 2.globl main

main:addi sp,sp,-16sw ra,12(sp)lui a0,%hi(string1)addi a0,a0,%lo(string1)lui a1,%hi(string2)addi a1,a1,%lo(string2)call printflw ra,12(sp)addi sp,sp,16li a0,0ret.section .rodata.balign 4

string1:.string "Hello, %s!\n"

string2:.string "world"

# Directive: enter text section# Directive: align code to 2^2 bytes# Directive: declare global symbol main# label for start of main# allocate stack frame# save return address# compute address of# string1# compute address of# string2# call function printf# restore return address# deallocate stack frame# load return value 0# return# Directive: enter read-only data section# Directive: align data section to 4 bytes# label for first string# Directive: null-terminated string# label for second string# Directive: null-terminated string

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AssembledHello.s:LinkableHello.o00000000 <main>: 0: ff010113 addi sp,sp,-16 4: 00112623 sw ra,12(sp) 8: 00000537 lui a0,0x0 # addr placeholderc: 00050513 addi a0,a0,0 # addr placeholder10: 000005b7 lui a1,0x0 # addr placeholder14: 00058593 addi a1,a1,0 # addr placeholder18: 00000097 auipc ra,0x0 # addr placeholder1c: 000080e7 jalr ra # addr placeholder20: 00c12083 lw ra,12(sp) 24: 01010113 addi sp,sp,16 28: 00000513 addi a0,a0,0 2c: 00008067 jalr ra

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LinkedHello.o:a.out000101b0 <main>: 101b0: ff010113 addi sp,sp,-16 101b4: 00112623 sw ra,12(sp) 101b8: 00021537 lui a0,0x21 101bc: a1050513 addi a0,a0,-1520 # 20a10 <string1> 101c0: 000215b7 lui a1,0x21 101c4: a1c58593 addi a1,a1,-1508 # 20a1c <string2> 101c8: 288000ef jal ra,0x10450 # 10450 <printf> 101cc: 00c12083 lw ra,12(sp) 101d0: 01010113 addi sp,sp,16 101d4: 00000513 addi a0,0,0101d8: 00008067 jalr ra

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LUI/ADDIAddressCalculationinRISC-VTargetaddressof<string1>is0x00020 A10InstructionsequenceLUI 0x00020,ADDI 0xA10 doesnotquiteworkbecauseimmediates inRISC-Varesignextended(and0xA10 hasa1inthehighorderbit)!

0x00020 000 + 0xFFFFF A10 = 0x0001F A10 (Offby0x00001000)Sowegettherightaddressifwecalculateitasfollows:

(0x00020 000 + 0x00001 000) + 0xFFFFF A10 = 0x00020 A10Whatis0xFFFFF A10?

Twoscomplementof0xFFFFF A10 =0x00000 5EF + 1 =0x00000 5F0 =1520tenSo0xFFFFF A10 =-1520ten

InstructionsequenceLUI 0x00021,ADDI -1520 calculates0x00020 A10

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Break!

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• ParallelRequestsAssignedtocomputere.g.,Search“Katz”

• ParallelThreadsAssignedtocoree.g.,Lookup,Ads

• ParallelInstructions>[email protected].,5pipelinedinstructions

• ParallelData>[email protected].,Addof4pairsofwords

• HardwaredescriptionsAllgates@onetime

• ProgrammingLanguages9/21/17 Fall2017 -- Lecture#9 17

SmartPhone

WarehouseScale

Computer

SoftwareHardware

HarnessParallelism&AchieveHighPerformance

LogicGates

Core Core…

Memory(Cache)

Input/Output

Computer

CacheMemory

Core

InstructionUnit(s) FunctionalUnit(s)

A3+B3A2+B2A1+B1A0+B0

Today

YouareHere! LevelsofRepresentation/Interpretation

lw $t0,0($2)lw $t1,4($2)sw $t1,0($2)sw $t0,4($2)

HighLevelLanguageProgram(e.g.,C)

AssemblyLanguageProgram(e.g.,RISC-V)

MachineLanguageProgram(RISC-V)

HardwareArchitectureDescription(e.g.,blockdiagrams)

Compiler

Assembler

MachineInterpretation

temp=v[k];v[k]=v[k+1];v[k+1]=temp;

0000 1001 1100 0110 1010 1111 0101 10001010 1111 0101 1000 0000 1001 1100 0110 1100 0110 1010 1111 0101 1000 0000 1001 0101 1000 0000 1001 1100 0110 1010 1111

LogicCircuitDescription(CircuitSchematicDiagrams)

ArchitectureImplementation

Anythingcanberepresentedasanumber,

i.e.,dataorinstructions

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Agenda

• SwitchingNetworks,Transistors• GatesandTruthTablesforCircuits• BooleanAlgebra• Logisim• AndinConclusion,…

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Agenda


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HardwareDesign

• Nextseveralweeks:howamodernprocessorisbuilt,startingwithbasicelementsasbuildingblocks

• Whystudyhardwaredesign?– Understandcapabilitiesandlimitationsofhwingeneralandprocessorsinparticular

– Whatprocessorscandofastandwhattheycan’tdofast(avoidslowthingsifyouwantyourcodetorunfast!)

– Backgroundformoreindepthhwcourses(CS152)– Hardtoknowwhatwillneedfornext30years– Thereisjustsomuchyoucandowithstandardprocessors:youmayneedtodesignowncustomhwforextraperformance– Evensomecommercialprocessorstodayhavecustomizablehardware!

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SynchronousDigitalSystems

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Synchronous:• Alloperationscoordinatedbyacentralclock

§ “Heartbeat”ofthesystem!

Digital:• Representallvaluesbytwodiscretevalues• Electricalsignalsaretreatedas1’sand0’s

•1and0arecomplementsofeachother• High/lowvoltagefortrue/false,1/0

Hardwareofaprocessor,suchastheRISC-V,isanexampleofaSynchronousDigitalSystem

Fall2017 -- Lecture#9

A Z

Switches:BasicElementofPhysicalImplementations

• Implementingasimplecircuit(arrowshowsactionifwirechangesto“1”orisasserted):

Z º A

A Z

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Closeswitch(ifAis“1”orasserted)andturnonlightbulb(Z)

Openswitch(ifAis“0”orunasserted)andturnofflightbulb(Z)


AND

OR

Z º A and B

Z º A or B

A B

A

B

Switches(cont’d)

• Composeswitchesintomorecomplexones(Booleanfunctions):

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HistoricalNote

• Earlycomputerdesignersbuiltadhoccircuitsfromswitches• Begantonoticecommonpatternsintheirwork:ANDs,ORs,…• Master’sthesis(byClaudeShannon)madelinkbetweenworkand19th CenturyMathematicianGeorgeBoole– Calledit“Boolean”inhishonor

• Couldapplymathtogivetheorytohardwaredesign,minimization,…

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Transistors

• Highvoltage(Vdd)represents1,ortrue• Lowvoltage(0voltsorGround)represents0,orfalse• Letthresholdvoltage(Vth)decideifa0ora1• Ifswitchescontrolwhethervoltagescanpropagatethroughacircuit,canbuildacomputer

• Ourswitches:CMOStransistors

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CMOSTransistorNetworks

• ModerndigitalsystemsdesignedinCMOS– MOS:Metal-OxideonSemiconductor– Cforcomplementary: usepairsofnormally-openandnormally-closedswitches• UsedtobecalledCOS-MOSforcomplementary-symmetry-MOS

• CMOStransistorsactasvoltage-controlledswitches– Similar,thougheasiertoworkwith,thanrelayswitchesfromearlierera– Useenergyprimarilywhenswitching

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n-channel transitoropen when voltage at Gate is low

closes when:voltage(Gate) > voltage (Threshold)

(High resistance when gate voltage Low,Low resistance when gate voltage High)


p-channel transistorclosed when voltage at Gate is low

opens when:voltage(Gate) > voltage (Threshold)

(Low resistance when gate voltage Low,High resistance when gate voltage High)

CMOSTransistors

• Threeterminals:source,gate,anddrain– Switchaction:ifvoltageongateterminalis(someamount)higher/lowerthansourceterminalthenconductingpathestablishedbetweendrainandsourceterminals(switchisclosed)

Gate

Source Drain

Gate

Source Drain

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Notecirclesymboltoindicate“NOT”or“complement”

Gate

DrainSource


CMOSCircuitRules• Don’tpassweakvalues=>UseComplementaryPairs

– N-typetransistorspassweak1’s(Vdd - Vth)– N-typetransistorspassstrong0’s(ground)– UseN-typetransistorsonlytopass0’s(Nfornegative)– ConverseforP-typetransistors:Passweak0s,strong1s

• Passweak0’s(Vth),strong1’s(Vdd)• UseP-typetransistorsonlytopass1’s(Pforpositive)

– UsepairsofN-typeandP-typetogetstrongvalues• Neverleaveawireundriven

– Makesurethere’salwaysapathtoVdd orgnd• NevercreateapathfromVdd tognd (ground)

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Agenda


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1v

X

Y 0 volts(gnd)

x y

1 volt(Vdd)

0v

what is the relationship

between x and y?

MOSNetworks

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p-channel transistorclosed when voltage at Gate is low

opens when:voltage(Gate) > voltage (Threshold)

n-channel transitoropen when voltage at Gate is low

closes when:voltage(Gate) > voltage (Threshold) Calledaninverterornotgate


x y z

0 volts

1 volt

0 volt

1 volt

0 volts

0 volts1 volt

1 volt

what is the relationship between x, y and z?

TwoInputNetworks

1v

X Y

0v

Z

1v

X Y

0v

Z

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x y z

0 volts

1 volt

0 volt

1 volt

0 volts

0 volts1 volt

1 volt

TruthTablesListoutputsforallpossibleinputs

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F Y

AB

CD

0

TruthTableExample#1:y=F(a,b):1iff a≠b

a b y0 0 00 1 11 0 11 1 0

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Y=AB+AB

Y=A+B

XOR

TruthTableExample#2:2-bitAdder

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HowManyRows?

+ C1

A1A0

B1B0

C2

C0

TruthTableExample#3:32-bitUnsignedAdder

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HowManyRows?

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7

TruthTableExample#4:3-inputMajorityCircuit

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Y=ABC+ABC+ABC+ABC

Y=BC+A(BC+BC)

Y=BC+A(B+C)

ThisiscalledSumofProductsform;JustanotherwaytorepresenttheTTasalogicalexpression

Moresimplifiedforms(fewergatesandwires)


CombinationalLogicSymbols

Z

AB Z

Z

A

AB

EasytoimplementwithCMOStransistors(theswitcheswehaveavailableandusemost)

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• Commoncombinationallogicsystemshavestandardsymbolscalledlogicgates

– Buffer,NOT

– AND,NAND

– OR,NOR

Agenda

• SwitchingNetworks,Transistors• GatesandTruthTablesforCircuits• BooleanAlgebra• Logisim ifthereistime• AndinConclusion,…

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BooleanAlgebra

• UseplusforOR– “logicalsum”

• UseproductforAND(a�b orimpliedviaab)– “logicalproduct”

• “Hat”tomeancomplement(NOT)• Thusab +a+c

= a�b +a+c= (aANDb)ORaOR(NOTc )

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BooleanAlgebra:Circuit&AlgebraicSimplification

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LawsofBooleanAlgebra

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XX=0X0=0X1=XXX=XXY=YX

(XY)Z=Z(YZ)X(Y+Z)=XY+XZ

XY+X=XXY+X=X+YXY=X+Y

X+X=1X+1=1X+0=XX+X=X

X+Y=Y+X(X+Y)+Z=Z+(Y+Z)X+YZ=(X+Y)(X+Z)

(X+Y)X=X(X+Y)X=XYX+Y=XY

ComplementarityLawsof0’sand1’s

IdentitiesIdempotentLawsCommutativityAssociativityDistribution

UnitingTheoremUnitedTheoremv.2DeMorgan’s Law

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BooleanAlgebraicSimplificationExample

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BooleanAlgebraicSimplificationExample

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ab c y00000011010001111001101111011111


system

datapath control

stateregisters

combinationallogicmultiplexer comparatorcode

registers

register logic

switchingnetworks

DesignHierarchy

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AConceptualRISC-VDatapath

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Administrivia

• Midterm#1NextTuesday:September26INCLASS!– ReviewsessionSaturday,September23:2-4pm@VLSB2050

• Approximatelyafourthofthetimededicatedtoreview• Restoftimewillbesolvingexam-levelquestions

–Midterm1roomassignmentswillbepostedonPiazza– Studentswhohaveanexamconflict:headTAStevenwillcontactyoubyemailwithyourtestingarrangements.

– Homework1Part2due11:59pmthisFriday– GuerrillaSessiontoday7-9pminCory540AB

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Break!

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Agenda

• SwitchingNetworks,Transistors• GatesandTruthTablesforCircuits• BooleanAlgebra• Logisim• StateMachines• AndinConclusion,…

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Logisim• Freeschematiccapture/logicsimulationprograminJava

– “Agraphicaltoolfordesigningandsimulatinglogiccircuits”– Searchanddownloadversion2.7.1,onlinetutorial– ozark.hendrix.edu/~burch/logisim/

• Drawinginterfacebasedontoolbar– Color-codedwiresaidinsimulatinganddebuggingacircuit– Wiringtooldrawshorizontalandverticalwires,automaticallyconnectingtocomponentsandtootherwires.

• Circuitlayoutsusedas"subcircuits"ofothercircuits,allowinghierarchicalcircuitdesign

• Includedcircuitcomponents:inputsandoutputs,gates,multiplexers,arithmeticcircuits,flip-flops,RAMmemory

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Logisim Wires• Bluewires:valueatthatpointis"unknown”• Graywires:notconnectedtoanything• OKwheninprocessofbuildingacircuit• Whenfinished=>wiresnotbeblueorgray• Ifconnected,allwiresshouldbegreen– Brightgreena1– Darkgreena0

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CommonMistakesinLogisim

• Connectingwirestogether• Usinginputforoutput• Connectingtoedgewithoutconnectingtoactualinput– Unexpecteddirectionofinput

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Agenda


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AndinConclusion,…• LinkingandLoading– Linkercombinestogetherseparatemodules,usingthesymbolandrelocationtablestoadjustaddressesasnecessary

– Loadermovesanexecutablefilefromdisktomemoryinallowitsexecution

• MultipleHardwareRepresentations– Analogvoltagesquantizedtorepresentlogic0andlogic1– Transistorswitchesformgates:AND,OR,NOT,NAND,NOR– Truthtablemappedtogatesforcombinationallogicdesign– Booleanalgebraforgateminimization

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L09 Hardware and State - inst.eecs.berkeley.edu

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