Boot block and POST debug code.docx

Boot block and POST debug code.docx

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BootblockandPOSTdebugcode

BootblockCheckpoints

D0

EarlyBootStrapProcessor（BSP）initializationlikemicrocodeupdate,

frequencyandotherCPUcriticalinitialization.Earlychipsetinitializationis

done.

D1

EarlysuperI/OinitializationisdoneincludingRTCandkeyboardcontroller.

Serialportisenabledatthispointifneededfordebugging.NMIisdisabled.

PerformkeyboardcontrollerBATtest.Savepower-onCPUIDvalueinscratch

CMOS.Gotoflatmodewith4GBlimitandGA20enabled.

D2

Verifythebootblockchecksum.Systemwillhanghereifchecksumisbad.

D3

DisableCACHEbeforememorydetection.Executefullmemorysizing

module.Ifmemorysizingmodulenotexecuted,startmemoryrefreshand

domemorysizinginBootblockcode.Doadditionalchipsetinitialization.

Re-enableCACHE.Verifythatflatmodeisenabled.

D4

Testbase512KBmemory.Adjustpoliciesandcachefirst8MB.Setstack.

D5

BootblockcodeiscopiedfromROMtolowersystemmemoryandcontrolis

giventoit.BIOSnowexecutesoutofRAM.Copiescompressedbootblock

codetomemoryinrightsegments.CopiesBIOSfromROMtoRAMforfaster

access.PerformsmainBIOSchecksumandupdatesrecoverystatus

accordingly.

D6

BothkeysequenceandOEMspecificmethodischeckedtodetermineifBIOS

recoveryisforced.IfBIOSrecoveryisnecessary,controlflowsto

checkpointE0.SeeBootblockRecoveryCodeCheckpointssectionof

documentformoreinformation.

D7

RestoreCPUIDvaluebackintoregister.TheBootblock-Runtimeinterface

moduleismovedtosystemmemoryandcontrolisgiventoit.Determine

whethertoexecuteserialflash.

D8

TheRuntimemoduleisuncompressedintomemory.CPUIDinformationis

storedinmemory.

D9

StoretheUncompressedpointerforfutureuseinPMM.CopyingMainBIOS

intomemory.LeavesallRAMbelow1MBRead-WriteincludingE000and

F000shadowareasbutclosingSMRAM.

DA

RestoreCPUIDvaluebackintoregister.GivecontroltoBIOSPOST

（ExecutePOSTKernel）.SeePOSTCodeCheckpointssectionofdocumentfor

moreinformation.

DC

SystemiswakingfromACPIS3state

E1-E8

EC-EE

OEMmemorydetection/configurationerror.Thisrangeisreservedfor

chipsetvendors&systemmanufacturers.Theerrorassociatedwiththis

valuemaybedifferentfromoneplatformtothenext.

2Pleasenotethatcheckpointsmaydifferbetweendifferentplatformsbasedonsystemconfiguration.

Checkpointsmaychangeduetovendorrequirements,systemchipsetoroptionROMsfromadd-inPCIdevices.

POSTCheckpoints

03

DisableNMI,Parity,videoforEGA,andDMAcontrollers.InitializeBIOS,

POST,Runtimedataarea.AlsoinitializeBIOSmodulesonPOSTentryand

GPNVarea.InitializedCMOSasmentionedintheKernelVariable

"wCMOSFlags."

04

CheckCMOSdiagnosticbytetodetermineifbatterypowerisOKandCMOS

checksumisOK.VerifyCMOSchecksummanuallybyreadingstoragearea.

IftheCMOSchecksumisbad,updateCMOSwithpower-ondefaultvalues

andclearpasswords.InitializestatusregisterA.

InitializesdatavariablesthatarebasedonCMOSsetupquestions.

Initializesboththe8259compatiblePICsinthesystem

05

Initializestheinterruptcontrollinghardware（generallyPIC）andinterrupt

vectortable.

06

DoR/WtesttoCH-2countreg.InitializeCH-0assystemtimer.Installthe

POSTINT1Chhandler.EnableIRQ-0inPICforsystemtimerinterrupt.

TrapsINT1Chvectorto"POSTINT1ChHandlerBlock."

07

FixesCPUPOSTinterfacecallingpointer.

08

InitializestheCPU.TheBATtestisbeingdoneonKBC.Programthe

keyboardcontrollercommandbyteisbeingdoneafterAutodetectionof

KB/MSusingAMIKB-5.

C0

EarlyCPUInitStart--DisableCache–InitLocalAPIC

C1

SetupbootstrapprocessorInformation

C2

SetupbootstrapprocessorforPOST

C5

Enumerateandsetupapplicationprocessors

C6

Re-enablecacheforbootstrapprocessor

C7

EarlyCPUInitExit

0A

Initializesthe8042compatibleKeyBoardController.

0B

DetectsthepresenceofPS/2mouse.

0C

DetectsthepresenceofKeyboardinKBCport.

0E

TestingandinitializationofdifferentInputDevices.Also,updatethe

KernelVariables.

TrapstheINT09hvector,sothatthePOSTINT09hhandlergetscontrolfor

IRQ1.Uncompressallavailablelanguage,BIOSlogo,andSilentlogo

modules.

13

EarlyPOSTinitializationofchipsetregisters.

20

RelocateSystemManagementInterruptvectorforallCPUinthesystem.

24

UncompressandinitializeanyplatformspecificBIOSmodules.GPNVis

initializedatthischeckpoint.

2A

InitializesdifferentdevicesthroughDIM.

SeeDIMCodeCheckpointssectionofdocumentformoreinformation.

2C

Initializesdifferentdevices.Detectsandinitializesthevideoadapter

installedinthesystemthathaveoptionalROMs.

2E

Initializesalltheoutputdevices.

31

AllocatememoryforADMmoduleanduncompressit.GivecontroltoADM

moduleforinitialization.InitializelanguageandfontmodulesforADM.

ActivateADMmodule.

33

Initializesthesilentbootmodule.Setthewindowfordisplayingtext

information.

37

Displayingsign-onmessage,CPUinformation,setupkeymessage,andany

OEMspecificinformation.

38

InitializesdifferentdevicesthroughDIM.SeeDIMCodeCheckpoints

sectionofdocumentformoreinformation.USBcontrollersareinitialized

atthispoint.

39

InitializesDMAC-1&DMAC-2.

3A

InitializeRTCdate/time.

3B

Testfortotalmemoryinstalledinthesystem.Also,CheckforDELorESC

keystolimitmemorytest.Displaytotalmemoryinthesystem.

3C

MidPOSTinitializationofchipsetregisters.

40

Detectdifferentdevices（Parallelports,serialports,andcoprocessorin

CPU,…etc.）successfullyinstalledinthesystemandupdatetheBDA,

EBDA…etc.

52

UpdatesCMOSmemorysizefrommemoryfoundinmemorytest.Allocates

memoryforExtendedBIOSDataAreafrombasememory.Programming

thememoryholeoranykindofimplementationthatneedsanadjustment

insystemRAMsizeifneeded.

60

InitializesNUM-LOCKstatusandprogramstheKBDtypematicrate.

75

InitializeInt-13andprepareforIPLdetection.

78

InitializesIPLdevicescontrolledbyBIOSandoptionROMs.

7CGenerateandwritecontentsofESCDinNVRam.

84

LogerrorsencounteredduringPOST.

85

Displayerrorstotheuserandgetstheuserresponseforerror.

87

ExecuteBIOSsetupifneeded/requested.Checkbootpasswordif

installed.

8C

LatePOSTinitializationofchipsetregisters.

8D

BuildACPItables（ifACPIissupported）

8E

Programtheperipheralparameters.Enable/DisableNMIasselected

90

Initializationofsystemmanagementinterruptbyinvokingallhandlers.

Pleasenotethischeckpointcomesrightaftercheckpoint20h

A1Clean-upworkneededbeforebootingtoOS.

A2

TakescareofruntimeimagepreparationfordifferentBIOSmodules.Fill

thefreeareainF000hsegmentwith0FFh.InitializestheMicrosoftIRQ

RoutingTable.Preparestheruntimelanguagemodule.Disablesthe

systemconfigurationdisplayifneeded.

A4

Initializeruntimelanguagemodule.Displaybootoptionpopupmenu.

A7

Displaysthesystemconfigurationscreenifenabled.InitializetheCPU’s

beforeboot,whichincludestheprogrammingoftheMTRR’s.

A9

Waitforuserinputatconfigdisplayifneeded.

AA

UninstallPOSTINT1ChvectorandINT09hvector.

AB

PrepareBBSforInt19boot.InitMPtables.

AC

EndofPOSTinitializationofchipsetregisters.De-initializestheADM

module.

B1

SavesystemcontextforACPI.PrepareCPUforOSbootincludingfinal

MTRRvalues.

00

PassescontroltoOSLoader（typicallyINT19h）.