Produtos da Marca Dell

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History

Inthemid‐1990sduringthedevelopmentofIntel’sItanium‐basedsystem,PCBIOSlimitations(forexample,16‐bit

processormode,1MBaddressablespace,PCAThardwaredependencies,etc.)hinderedplatformdevelopmentfor

Itanium.WhiletheItaniumchipwasnotwellreceived,thedevelopmentexposedsignificantlimitationstothe

originalPCfirmwarearchitecturethatledtothedevelopmentofanewframework,calledExtensibleFirmware

Interface(EFI).

In2005,severalleadingtechcompaniescametogethertocreatetheEFIForum.BasedonEFIarchitecture,the

UEFIForum’smissionwastocreatethefirsteverindustrystandardfirmwareinterfacespecification–Unified

ExtensibleFirmwareInterface(UEFI).DellisrepresentedontheboardofdirectorsoftheUEFIForum.

WhatisUEFI?

TheUEFIspecificationdefinesaninterfacebetweenoperatingsystemsandplatformfirmware.Theinterface

consistsofdatatablesthatcontainplatform‐relatedinformation,plusbootandruntimeservicecallsthatare

availabletotheoperatingsystemanditsloader.

Together,theseprovideastandard,modern

environmentforbootinganoperatingsystemand

runningpre‐bootapplications.

Inadditiontotheservices,UEFIdefinesvarious

protocols/APIstoaccessvarioushardwareandthe

bootdevicesinthesystem.TheUEFIspecificationalso

definesadrivermodelthatisgenericandcanbe

adaptedtoanytypeofbusordevice.TheUEFIDriver

Model

isdesignedtosupporttheexecutionof

modularpiecesofcode,knownasdrivers,thatrunin

theprebootenvironment.Thesedriversmaymanage

orcontrolhardwarebusesanddevicesonthe

platform,ortheymayprovidesomesoftware‐derived,

platform‐specificservice.

Thereare3typesofentitiesthatcan

executeunderUEFIenvironment:

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• Applications:SomeexamplesofcommonEFIapplicationsincludetheEFIshell,EFIshell

commands,flashutilities,anddiagnosticutilities.ItisperfectlyacceptabletoinvokeEFI

applicationsfrominsideotherEFIapplications.

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• OperatingSystemLoader:AspecialtypeofEFIapplication,calledan

operatingsystemboot

loader,providesthenecessaryinitializationroutinesuntilthethisloaderhassetupenoughof

theoperatingsysteminfrastructuretobereadytoassumeownershipofthesystemresources.

Oncetheoperatingsystemassumescontrol,theEFIcorefreesallofitsboottimeservicesand

drivers,

leavingonlytherun‐timeservicesanddrivers.

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• Drivers:EFIdriversdifferfromEFIapplicationsinthatthedriverstaysresidentinmemoryunless

anerrorisreturnedfromthedriver'sentrypoint.TheEFIcorefirmware,thebootmanager,or

otherEFIapplicationsmayloaddrivers.