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1、What'stheDifferenceBetweenUSBUASPAndBOTUSB3.0offersapproximately10:1performanceimprovementoverUSB2.0,butrealizingthefullpotentialofthatgainformassstoragedevicesposesadditionalchallenges.ThemainstayofmassstoragestandardsforUSB2.0and1.1hasbeentheBulkOnlyTranspo
2、rt(BOT)deviceclassspecificationforUSB,andithasservedthepersonalcomputerindustrywellwithitssimplicityandmodestefficiency.Ithasproventobesimpleandinexpensivetoimplementinmicroprocessor-basedsystems,includingpersonalcomputers,andhencesuitableforinexpensiveflash-
3、basedmassstoragedevices.InBulkOnlyTransport,standardUSBBulktransactionsareusedforeachstageofamassstoragetransfer-command,data,andstatus.Infact,earlyversionsoftheBOTstandardreferredtoitas"BBB,"shortforBulk/Bulk/Bulk,whichwasanenhancementovertheolderControl/Bul
4、k/Interrupt(CBI)standardthatwasused(andstillis)mainlyforfull-speedUSBfloppydiskdrives.HigherperformancemassstoragedevicestendtousetheSCSIstandards(SmallComputerSystemInterface),whichallowdevicestosupportperformance-enhancingmodesofoperationsuchasmultipleoutst
5、andingrequestsandout-of-orderrequestcompletions.Multipleoutstandingrequestsmeanthatthesystemdoesn'tneedtowaitforeachrequesttobecompletedbeforethenextrequestcanbesenttothedevice.Thedevicesimplystorestherequestsinitsownbuffer,sendsacompletionbacktothehostaseach
6、requestiscompleted,andstartsworkingonthenextrequestinthebufferassoonasthepreviousoneiscompleted.ThisallowsthedevicetobemorefullyutilizediftheUSBlinkcankeepupwiththeadditionalbustraffic,asUSB3.0finallycan.ButtheoriginalBOTstandardhadnoprovisionforsupportingmul
7、tipleoutstandingrequests.AnewUSBstandardwasneeded,andwithUSB3.0therehasbeenanewindustryinitiativetoprovideanimprovedmassstorageclassspecification.ThenewclassstandardisknownasUAS(USBAttachedSCSI)andUASP(UASProtocol).TheUASstandardisdevelopedandmaintainedbytheT
8、10TechnicalCommitteeintheANSIorganization(AmericanNationalStandardsInstitute),undertheauspicesoftheINCITS(InternationalCommitteeonInformationTechnologyStandards)withinANSI.TheT10Committee
