会员注册 | 登录 | 微信快捷登录 支付宝快捷登录 QQ登录 微博登录 | 帮助中心 人人文库renrendoc.com美如初恋!
站内搜索 百度文库

热门搜索: 直缝焊接机 矿井提升机 循环球式转向器图纸 机器人手爪发展史 管道机器人dwg 动平衡试验台设计

30-Structural aspects of the System 360 Model 85, Part II The cache.pdf30-Structural aspects of the System 360 Model 85, Part II The cache.pdf -- 5 元

宽屏显示 收藏 分享

资源预览需要最新版本的Flash Player支持。
您尚未安装或版本过低,建议您

Thecache,ahighspeedbufferestablishingastoragehierarchyintheModel85,isdiscussedindepthinthispart,sinceitrepresentsthebasicorganizationaldeparturefromotherSYSTEM/BOcomputers.Discussedareorganizationandoperationofthecache,includingthemechanismsusedtolocateandretrievedataneededbytheprocessor.Theinternalperformancestudiesthatledtouseofthecachearedescribed,andsimulatedperformanceofthechosenconfigurationiscomparedwiththatofatheoreticalsystemhavinganentire80nanosecondmainstorage.Finally,theeffectsofvaryingcacheparametersarediscussedandtabulated.StructuralaspectsoftheSystem/360Model8511ThecachebyJ.S.LiptayAmongtheobjectivesoftheModel85isthatofprovidingaSYSTEM/compatibleprocessorwithbothhighperformanceandhighthroughput.OneoftheimportantingredientsofhighthroughputisalargemainstoragecapacityseetheaccompanyingarticleinPartI.However,itisnotfeasibletoprovidealargemainstoragewithanaccesstimecommensuratewiththe80nanosecondprocessorcycleoftheModel85.Alongeraccesstimecanbepartiallycompensatedforbyanincreaseinoverlap,greaterbuffering,deeperstorageinterleaving,moresophisticationinthehandlingofbranches,andotherimprovementsintheprocessor.Allofthesefactorsonlypartiallycompensatefortheslowerstorage,and,therefore,wedecidedtouseastoragehierarchyinstead.Thestoragehierarchyconsistsofa1.04microsecondmainstorageandasmall,faststorecalledacache,lwhichisintegratedintotheCPU.Thecacheisnotaddressablebyaprogram,butratherisusedtoholdthecontentsofthoseportionsofmainstoragethatarecurrentlybeingused.Mostprocessorfetchescanthenbehandledbyreferringtothecache,sothatmostofthetimetheprocessorhasashortaccesstime.Whentheprogramstartsoperatingondatainadifferentportionofmainstorage,thedatainthatportionmustbeloadedintothecacheandthedatafromsomeotherportionremoved.Thisactivitymusttakeplacewithoutprogramassistance,sincetheModel85mustbecompatiblewiththerestofThispaperdiscussesorganizationofthecacheandthestudiesthatledtoitsuseintheModel85andtoselectingofvaluesforitsparameters.theSYSTEM/360line.ZBMSYSTEMSJOURNALVOL.7NO.1196815Figure1AssignmentofcachesectorstomainstoragesectorsMAINSTORAGECacheorganizationThemainstorageunitsthatcanbeusedontheModel85aretheIBM23655andthe2385.Theyhavea1.04microsecondcycletimeandmakeavailablecapacitiesfrom512Kbytesto4096KbytesK1024.Thecacheisa16Kbyteintegratedstorage,whichiscapableofoperatingeveryprocessorcycle.Optionally,itcanbeexpandedto24Kbytesor32Kbytes.Boththecacheandmainstoragearelogicallydividedintosectors,eachconsistingof1Kcontiguousbytesstartingon1Kbyteboundaries.Duringoperation,acorrespondenceissetupbetweencachesectorsandmainstoragesectorsinwhicheachcachesectorisassignedtoasingledifferentmainstoragesector.However,becauseofthelimitednumberofcachesectors,mostmainstoragesectorsdonothaveanycachesectorsassignedtothemseeFigure1.Eachofthecachesectorshasa14bitsectoraddressregister,whichholdstheaddressofthemainstoragesectortowhichitisassigned.Theassignmentofcachesectorsisdynamicallyadjustedduringassigningoperation,sothattheyareassignedtothemainstoragesectorsthatcachearecurrentlybeingusedbytheprogram.Iftheprogramcausesasectorsfetchfromamainstoragesectorthatdoesnothaveacachesectorassignedtoit,oneofthecachesectorsisthenreassignedtothatmainstoragesector.Tomakeagoodselectionofacachesectortoreassign,enoughinformationismaintainedtoorderthecachesectorsintoanactivitylist.Thesectoratthetopofthelististheonethatwasmostrecentlyreferredto,thesecondoneisthenextmostrecentlyreferredto,andsoforth.Whenacachesectorisreferredto,itismovedtothetopofthelist,andtheinterveningonesaremoveddownoneposition.Thisisnotmeanttoimplyanactualmovementofsectorswithinthecache,butratherreferstoalogical16J.8.LIPTAYorderingofthesectors.Whenitisnecessarytoreassignasector,theoneselectedistheoneatthebottomoftheactivitylist.Thiscachesectoristheonethathasgonethelongestwithoutbeingreferredto.Whenacachesectorisassignedtoadifferentmainstoragesector,thecontentsofallofthe1Kbyteslocatedinthatmainstoragesectorarenotloadedintothecacheatonce.Rather,eachsectorisdividedinto16blocksof64bytes,andtheblocksareloadedonademandbasis.Whenacachesectorisreassigned,theonlyblockthatisloadedistheonethatwasreferredto.Iftheyarerequired,theremainingblocksareloadedlater,oneatatime.Eachblockinthecachehasabitassociatedwithittorecordwhetherithasbeenloaded.Thisvaliditybitisturnedonwhentheblockisloadedandoffwhenthesectorisreassigned.Storeoperationsalwayscausemainstoragetobeupdated.Ifthemainstoragesectorbeingchangedhasacachesectorassignedtoit,thecacheisalsoupdatedotherwise,noactivityrelatedtothecachetakesplace.Therefore,storeoperationscannotcauseacachesectortobereassigned,ablocktobeloaded,ortheactivitylisttoberevised.Sinceallofthedatainthecacheisalsoinmainstorage,itisnotnecessaryonacachesectorreassignmenttomoveanydatafromthecachetomainstorage.Allthatisrequiredistochangethesectoraddressregister,resetthevaliditybits,andinitiateIoadingofablock.Theprocessoriscapableofbufferingoneinstructionrequestingthestoringofinformationinmainstorage,sothatitcanproceedwithsubsequentinstructionsevenifexecutionofthestoreinstructioncannotbeinitiatedimmediately.Twoprocessorcyclesarerequiredtofetchdatathatisinthecache.Thefirstcycleisusedtoexaminethesectoraddressregistersandthevaliditybitstodetermineifthedataisinthecache.Thesecondcycleisthenusedtoreadthedataoutofthecache.However,requestscannormallybeoverlapped,sothatonerequestcanbeprocessedeverycycle.Ifthedataisnotpresentinthecache,additionalcyclesarerequiredwhiletheblockisloadedintothecachefrommainstorage.ThestoragewordsizeonwhichtheModel85operatesinternallyis16bytes.Thisisthewidthofthedatapathstoandfromthestorageunits,andistheamounttheprocessorcanstoreorfetchwithasinglerequest.Becauseasingle23655storageunitoperatesonan8bytewideinterface,twounitsarepairedtogetherandoperatedsimultaneously.Exceptforthe512Kconfiguration,mainstorageisinterleavedfourways.Sinceablockis64bytes,fourfetchestomainstoragearerequiredtoloadoneblockintothecache.Withfourwayinterleaving,thismeansonerequesttoeachbasicstoragemodule.Toimproveperformance,thefirstbasicstoragemodulereferredtoduringeachblockloadistheonecontainingthe16byteswantedbytheprocessor.Inadditiontobeingloadedintothecache,thedataissentdirectlytotheprocessor,sothatexecutioncanproceedassoonaspossibleseeFigure2.OntheModel85,channelsstoreandfetchdatabywayoftheMODEL85CACHEFigure2TimingforablockloadMAINSTORAGENttUtUBSMZACCESSTIMEIBSMPIBSMOACCESSTIMEwBSMBASICSTORAGEMODULEprocessor.Channelfetchesareprocessedbygettingtherequireddatafrommainstoragewithoutreferringtothecache.Channelstoresarehandledthesamewayasprocessorstores.Inthisway,ifachannelchangesdatathatisinthecache,thecacheisupdatedbutthechannelsdonothaveanypartofthecachedevotedtothem.PerformancestudiesAmongthequestionsthathadtobeansweredtodeterminewhetherthecacheapproachshouldbetakenwere1howeffectiveisit,and2doesitseffectivenessvarysubstantiallyfromoneprogramtoanotherTheprincipaltoolsusedtoanswerthesequestionsarethetracingandtimingtechniquesreferredtoinPartI.ThetracingtechniqueproducesaninstructionbyinstructiontraceofaprogramoperatingundertheSYSTEM/OOperatingSystem.Theoutputisasequenceoftracetapes,whichcontaineveryinstructionexecuted,whetherintheproblemprogramortheoperatingsystem,andthenecessaryinformationtodeterminehowlongittakestobeexecuted.Thesetracetapescontainabout250,000instructionseachandareusedasinputtoatimingprogram,whichdetermines,cyclebycycle,howtheModel85wouldexecutethatsequenceofinstructions.Thesetechniquesareintendedtodetermineinternalperformanceanddonotprovideanyinformationconcerningthroughput.Anintensiveinvestigationprecededselectionoftheprogramsusedinthisstudy.Inordertomeasuretheeffectivenessofthecache,wepostulatedcacheasystemidenticaltotheModel85exceptthatthestoragehierarchyeffectivenessisreplacedbyasinglelevelstorageoperatingatcachespeed.TheperformanceofsuchasystemisthatwhichwouldbeachievedbytheModel85ifitalwaysfoundthedataitwantedinthecacheandifitneverencounteredinterferenceinmainstorageduetostores.Therefore,itrepresentsanupperlimitontheperformanceoftheModel85howclosetheModel85approachesthisidealcanserveasameasureofhoweffectivethecacheis.NineteentracetapesI18J.s.LIPTAYFigure3Model85performancerelativetosinglelevelstorageoperatingatcachespeedMEAN8175.79808490.94PERCENTAGEOFIDEALPERFORMANCEFlgure4ProbabilityoffindingfetcheddataincachePROBABILITYweretimedforboththeModel85andthepostulatedsystem,andtheperformanceoftheModel85wasexpressedasapercentageoftheperformanceoftheidealsystem.Figure3showsthedistributionofperformancedataobtained,Theaveragewas81percentoftheperformanceoftheidealsystem,witharangebetween66and94percent.Animportantstatisticrelatedtocacheoperationistheprobabilityoffindingthedatawantedforafetchinthecache.Figure4showsthedistributionofthisprobabilityforthesame19tracetapesusedforFigure3.Theaverageprobabilitywas0.968.Itisworthnotingthat,iftheaddressesgeneratedbyaprogramwererandom,theprobabilityoffindingthedatawantedinthecachewouldbemuchlessthan0.01.Therefore,itcanbesaidthatwhatmakesthecacheworkisthefactthatrealprogramsarenotrandomintheiraddressingpatterns.MODEL85CACHETable2AverageperformancerelativetoanidealsystemwithcachesizeandnumberofbytesperblockvariedNumberofsectors16NumberofNumberofbytesperblockcachebytes64128266,8K0.74416K0.8250.8100.78132K0.8910.8850.870Table3Comparativeperformanceusingdifferentcachesectorreplacementalgorithmsalgorithmperformance1partition1.0002partitions0.9904partitions0.9878partitions0.97916partitions0.933usagebits0.931ReplacementalgorithmchosenfortheModel85Table3summarizestheresultsobtained.Thechoiceoftheactivitylistwasmadebecauseitprovidedthebestbalancebetweencostandperformance.SummarycommentTheinclusionofastoragehierarchyrepresentsoneofthemajoradvancesinsystemorganizationpresentintheModel85.Althoughtheconceptofastoragehierarchyisnotnew,thesuccessfulimplementationofananosecond/microsecondlevelofhierarchywasinhibiteduntilnowbythelackofasuitabletechnology.AsimplementedintheModel85,thefastmonolithicstoragephysicallyintegratedwiththeCPUlogicyieldsthedesiredmachinespeed,whilethelargecorestorageyieldsthedesiredstoragecapacity,thecombinationbeingtransparenttotheuser.Itislikelythatwithfutureprogressintechnologythisnanosecond/microsecondhierarchyisnotmerelyaninnovationthatworkedoutwellfortheModel85,butratheritisafundamentalstepforwardthatwillbeincorporatedintomostlargesystemsofthefuture.CITEDREFREENCEANDFOOTNOTE1.Thetermcacheissynonymouswithhighspeedbuffer,asusedinotherModel85documentation.2.D.H.Gibson,Considerationsinblockorientedsystemsdesign,AFZPSConferenceProceedings,SpringJointComputerConference30,AcademicPress,NewYork,NewYork,75801967.MODEL85CACHE21
编号:201401051948176808    大小:412.87KB    格式:PDF    上传时间:2014-01-05
  【编辑】
5
关 键 词:
工业、机械、能源、设计、建模、模具、工学
温馨提示:
1: 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
2: 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
3.本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
5. 人人文库网仅提供交流平台,并不能对任何下载内容负责。
6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
  人人文库网所有资源均是用户自行上传分享,仅供网友学习交流,未经上传用户书面授权,请勿作他用。
0条评论

还可以输入200字符

暂无评论,赶快抢占沙发吧。

当前资源信息

4.0
 
(2人评价)
浏览:10次
baixue100上传于2014-01-05

官方联系方式

客服手机:13961746681   
2:不支持迅雷下载,请使用浏览器下载   
3:不支持QQ浏览器下载,请用其他浏览器   
4:下载后的文档和图纸-无水印   
5:文档经过压缩,下载后原文更清晰   

相关资源

相关资源

相关搜索

工业、机械、能源、设计、建模、模具、工学  
关于我们 - 网站声明 - 网站地图 - 友情链接 - 网站客服客服 - 联系我们
copyright@ 2015-2017 人人文库网网站版权所有
苏ICP备12009002号-5