Energy Efficient Datapath Scheduling using Multipl

1、EnergyEfﬁcientDatapathSchedulingusingMultipleVoltagesandDynamicClockingSarajuP.MohantyN.RanganathanDept.ofComp.ScienceandEng.Dept.ofComp.ScienceandEng.UniversityofNorthTexas,TX76203.UniversityofSouthFlorida,FL33620.E-mail:smohanty@cs.unt.eduE-mail:ranganat@csee.usf.eduRecently,dynamicfrequencyscalinghasbeenexploredattheCPUandsystemlevelsforpoweroptimization.Lowpowerdatapathschedulingusingmultiplesupplyvoltageshasbeenwellresearched.Inthiswork,wedevelopnewdatapathschedulingalgorithmsthatusemultip。

2、lesupplyvoltagesanddynamicfrequencyclockinginaco-ordinatedmannerinordertoreduceenergyconsumptionofdatapathcircuits.Indynamicfrequencyclocking,thefunctionalunitscanbeoperatedatdifferentfrequenciesdependingonthecomputationsoccurringwithinthedatapathduringagivenclockcycle.Thestrategyistoschedulehighenergyunits,suchasmultipliersatlowerfrequenciessothattheycanbeoperatedatlowervoltagestoreduceenergyconsumptionandthelowenergyunits,suchasaddersathigherfrequencies,tocompensateforspeed.Theproposedtimeandr。

3、esourceconstrainedalgorithmshavebeenappliedtovarioushighlevelsynthesisbenchmarkcircuitsunderdifferenttimeandresourceconstraints.Theexperimentalresultsshowsigniﬁcantreductioninenergyforboththealgorithms.CategoriesandSubjectDescriptors:B.5.1[Register-Transfer-LevelImplementation]:DatapathDesign;B.5.2[Register-Transfer-LevelImplementation]:AutomaticSynthesis,Optimization;B.7.1[TypesandDesignStyles]:VLSI(verylargescaleintegration)GeneralTerms:Algorithms,Performance,Design,Reliability,Scheduling,Time。

4、ComplexityAdditionalKeyWordsandPhrases:High-Levelsynthesis,low-powerdatapathsynthesis,multiplevoltageschedul-ing,timeconstrainedscheduling,resourceconstrainedschedulinganddynamicfrequencyclocking1.INTRODUCTIONWiththeincreaseindemandforpersonalcomputingdevicesandwirelesscommunicationsequipment,thedemandforsynthesizinglowpowerconsumingcircuitshasincreased.Theneedforlowpowersynthesisisdrivenbyseveralfactors,suchas[Pedram1996],demandofportablesystems(batterylife),thermalconsiderations(coolingandpack。

5、agingcosts),environmentalconcerns(useofnaturalresources),andreliabilityissues.Whileenergyconsumptionofadevicehastobeminimumtoincreasebatterylife,theenergy-delay-producthastobeminimizedtoincreasebatterylifeandtoreducedelay,simultaneously.LetusconsiderthefollowingequationsforaCMOScircuit[BurdandBrodersen1995;ThisresearchwascarriedoutattheDepartmentofComputerScienceandEngineering,UniversityofSouthFlorida,Tampa,FL33620.Permissiontomakedigital/hardcopyofallorpartofthismaterialwithoutfeeforpersonalorc。

6、lassroomuseprovidedthatthecopiesarenotmadeordistributedforproﬁtorcommercialadvantage,theACMcopyright/servernotice,thetitleofthepublication,anditsdateappear,andnoticeisgiventhatcopyingisbypermissionoftheACM,Inc.Tocopyotherwise,torepublish,topostonservers,ortoredistributetolistsrequirespriorspeciﬁcpermissionand/orafee.c2004ACM1084-4309/2004/0400-0111$5.00ACMTransactionsonDesignAutomationofElectronicSystems,Vol.V,No.N,August2004,Pages111–133.112MohantyandRanganathanPouwelseetal.2001b]:—Energydiss。

7、ipationperoperationis(1)where,istheeffectiveswitchedcapacitanceandisthesupplyvoltage,—Forfrequency,thepowerdissipationfortheoperationis(2)—Further,thecriticaldelay()inadevicethatdeterminesthemaximumfrequency()isbelow,where,isthethresholdvoltage,!isatechnologydependentfactorandisaconstant.#%$’&)((3)Fromtheabovethreeequations,thefollowingcanbededuced[BurdandBrodersen1995;Pouwelseetal.2001b;Peringetal.2000;MartinandSiewiore。

8、k2001]:—Reducingonly,bothenergyandpowercanbesavedatthecostofperformance.—Slowingdownthecircuitbyreducingonlywillsavepowerbutnotenergy.—However,byscalingfrequencyandvoltageinacoordinatedmanner,bothenergyandpowercanbesavedwhilemaintainingperformance.Thethirdfactoraboveformsthemajormotivationforthiswork.Theobjectiveistogener-ateadatapathschedulethatattemptsatenergyandpowerreductionwithoutdegradingtheperformancebyusingmultiplevoltagesanddynamicfrequencyinaco-ordinatedmanner.Inthispaper,weconsid。

9、ertheuseofdynamicfrequencyclockingorfrequencyscalingalongwithmultiplesupplyvoltagesforsynthesisoflowpowerdatapathcircuitsusefulforsignalprocessingapplications.Indynamicfrequencyclocking(hereto,willbereferredtoasDFC),thefunctionalunitscouldoperateatdifferentspeedsduringeachclockcycledependingontheunitsactiveinthatcycle.Wedeveloptwonewdatapathschedulingalgorithms,onereferredtoasTC-DFC(timeconstrained)andotherreferredtoasRC-DFC(resourceconstrained),bothofwhichaimatreducingenergyconsumption.Theresou。

10、rceconstraintsconsistofthenumberandtypeofeachfunctionalunit,theallowedvoltagesandfrequencies.Thetimeconstraintisdeﬁnedintermsofmultiplesofthecriticalpathdelayofthedatapathcircuit.RC-DFCminimizesthetotalenergyconsumptionofthedatapathcircuitbymaximizingtheutilizationoflowersupplyvoltageresourcesfromthegivensetsofresourcesoperatingatdifferentsupplyvoltageswhilereducingthetimepenalty.Ontheotherhand,TC-DFCminimizesthetotalenergyconsumptionofthedatapathcircuitwithoutviolatingthetimingconstraintsassumin。