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ANOTHER COMPUTER KNOWLEDGE SITE : CROY WORLD PRODUCTIONS
BOOT SEQUENCES

REGARDLESS OF THE OPERATING SYSTEM, POST ( POWER ON SELF TEST ) IS ALWAYS PERFORMED FIRST IN THE BOOT SEQUEMCE.

POST

POST IS THE DIAGNOSTIC TESTING SEQUENCE THAT A COMPUTERS BASIC INPUT/OUTPUT SYSTEM OR STARTING PROGRAM AUTOMATICALLY RUNS. THE ACTUAL TESTS CAN DIFFER DEPENDING ON HOW THE BIOS IS CONFIGURED. BUT USUALLY POST TEST THE RANDOM ACCESS MEMORY, KEYBOARD, DISK DRIVES, AND OTHER HARDWARE. TO MAKE SURE THEY ARE WORKING PROPERLY. IF THE TEST ARE SUCCESSFUL, THE COMPUTER BOOTS ITSELF. IF THE TEST ARE UNSUCCESSFUL, THE COMPUTER REPORTS THE ERROR BY A SERIES OF BEEPS OR BY DISPLAYING ERROR MESSAGES AND CODES ON THE DISPLAY SCREEN.

WINDOWS 9X BOOT SEQUENCE :

1) AFTER THE BIOS PERFORMS THE POST, AND IF THE PC HAS A PLUG AND PLAY BIOS, PLUG AND PLAY DEVICES ARE CONFIGURED.

2) THE PARTITION TABLE IS ACCESSED, AND THE BOOT RECORD ACTIVATES IO.SYS.

3) THE WINDOWS 9X BOOT SEQUENCE PERFORMS PARTIALLY IN REAL MODE AND THEN SWITCHES TO PROTECTED MODE. BEGINNING AT THIS POINT, THE BOOT SEQUENCE PERFORMS IN REAL MODE.

4) THE MSDOS.SYS IS CHECKED FOR ANY WINDOWS PARAMETERS ( SUCH AS BOOTMULTI OR BOOTMENU ).

5) IF ALL IS NORMAL, THE MESSAGE STARTING WINDOWS 95 DISPLAYS OR THE WINDOWS 98 SPLASH SCREEN IS DISPLAYED. THE SYSTEM PAUSES FOR TWO SECONDS TO WAIT FOR A FUNCTION KEY TO CHANGE THE BOOT PATH.

6) IF FILE COMPRESSION IS IN USE, DRVSPACE.BIN LOADS.

7) THE REGISTRY ( SYSTEM.DAT ) IS CHECKED, AND IF ITS VALID, IT LOADS.

8) WINDOWS 9X PERFORMS HARDWARE DETECTION AND IDENTIFIES ANY NEW HARDWARE.

9) IO.SYS PROCESSES THE COMMANDS IN THE CONFIG.SYS AND AUTOEXEC.BAT FILES, IF THEY EXIST.

10) BOOT SEQUENCE SWITCHES TO PROTECTED MODE.

11) WIN.COM EXECUTES.

12) THE VMM32.VXD FILE AND ALL VIRTUAL DEVICE DRIVERS INCLUDED IN THE REGISTRY OR THE SYSTEM.INI FILE LOAD.

13) WINDOWS 95 CORE COMPONENTS - KERNEL, GDI, AND USER - LOAD ALONG WITH THE EXPLORER AND NETWORK SUPPORT.

14) ANY APPLICATIONS IN THE STARTUP ( RUNONCE) SECTION OF THE REGISTRY START.

15) THE BOOT SEQUENCE ENDS.

WINDOWS 2000 BOOT SEQUENCE

1) OPERATING SYSTEM, THE BOOTSTRAP LOADER PROGRAM NTLDR IS THE KEY COMPONENT OF THIS STEP. IT WILL USE THE FILES Ntdetect.com, boot.ini, and bootsect.dos ( FOR DUAL BOOT COMPUTERS ) AT THE BEGINNING OF THIS STEP, THE SCREEN WILL DISPLAY THE OS LOADER V5.0 MESSAGE ON THE SCREEN. WHEN NTLDR RUNS, IT SWITCHES THE PROCESSOR INTO 32 BIT FLAT MEMORY MODE ( UNTIL THIS POINT THE COMPUTER WAS RUNNING IN REAL MODE. IT THEN STARTS THE APPROPRIATE MINI-FILE ( e.g.:FAT, NTFS ),SO IT CAN READ THE FILES FROM THE DISK. IT WILL THEN READ THE Boot.ini FILE, AND DISPLAY THE BOOT MENU ON THE SCREEN. IF AN OPERATING SYSTEM OTHER THAN WINDOWS 2000 IS SELECTED, NTLDR THEN LOADS THE bootsect.dos FILE AND PASSES CONTROL TO IT, WHICH THEN BOOTS THE OPERATING SYSTEM. IF WINDOWS 2000 IS SELECTED, THEN NTLDR RUNS Ntdetect.com TO GATHER INFORMATION ABOUT THE COMPUTERS HARDWARE. IT IS ALSO IN THIS STEP WHEN YOU CAN CHOOSE TO PRESS THE F8 FOR TROUBLESHOOTING AND ADVANCED STARTUP OPTIONS. ONCE Ntdetect.com HAS COLLECTED THE HARDWARE INFORMATION, NTLDR WILL LOAD Ntoskrnl AND PASS THAT INFORMATION TO IT.

2) KERNEL LOAD , THIS STEP BEGINS WITH THE LOADING OF Ntoskrnl.exe, ALONG WITH THE hall.dll.NTLDR WILL ALSO READ THE SYSTEM REGISTRY KEY INTO MEMORY, AND SELECT THE HARDWARE CONFIGURATION AND CONTROL SET ( FROM THE REGISTRY ) THAT WILL BE USED FOR THIS BOOT. IF YOU HAVE MORE THAN ONE HARDWARE PROFILE CREATED, YOU COULD SELECT IT AT THIS POINT IN THE BOOT SEQUENCE. NTLDR WILL ALSO LOAD ANY DEVICE DRIVERS THAT HAVE A START VALUE ( AGAIN FROM THE REGISTRY ) OF OXO. IF YOU ADD THE SWITCH /SOS IN THE boot.ini, YOU WILL BE ABLE TO SEE THE DRIVERS LISTED ON THE SCREEN AS THEY ARE LOADED. AT THIS POINT ALL OF THESE FILES HAVE BEEN LOADED INTO MEMORY.

3) KERNEL INITIALIZATION. ONCE Ntoskrnl.exe IS INITIALIZED, IT CREATES THE CLONE CONTROL SET BY COPYING THE CURRENT CONTROL SET. IT WILL ALSO CREATE THE HARDWARE KEY IN THE REGISTRY USING THE INFORMATION GATHER EARLIER BY THE ntdetect.com. Ntoskrnl.exe WILL THEN INITIALIZE THE DRIVERS LOADED EARLIER, AND WILL THEN SCAN THE REGISTRY FOR DEVICE DRIVERS THAT HAVE A START VALUE OF OX1.

4) SERVICES LOAD. THIS STEP BEGINS WITH THE STARTING OF THE SESSION MANAGER ( Smss.exe ). IT WILL RUN THE PROGRAMS LISTED IN ITS BOOTEXECUTE REGISTRY ENTRY, AS WELL AS STARTING THE REQUIRED SUBSYSTEMS. THE WIN32 SUBSYSTEM WILL THEN START Winlogon.exe, WHICH STARTS THE LOCAL SECURITY ADMINISTRATION ( Lsass.exe ) AND THE Ctrl + Alt + Delete WINDOW APPEARS. THE SERVICE CONTROLLER ( Screg.exe ) WILL CHECK THE REGISTRY FOR SERVICES WITH A START VALUE OF OX2, AND WILL LOAD THEM. SERVICES CAN BE LOADED SIMULTANEOUSLY, BUT DEPENDENT ON THEIR DEPENDENCIES. SERVICES WITH START VALUES OF OX3 ARE STARTED MANUALLY, AND SERVICES WITH START VALUES OF OX4 ARE DISABLED.

5) LOGON. THE LOGON PROMPT WILL APPEAR DURING THE PREVIOUS STEP, BUT IT BEGINS THE FINAL STEP IN THE BOOT PROCESS. A BOOT IS NOT CONSIDERED SUCCESSFUL OR COMPLETED UNTIL A USER LOGS IN. AFTER A SUCCESSFUL LOGON, THE CLONE CONTROL SET FROM STEP 3 IS COPIED TO THE LASTKNOWNGOOD CONTROL SET. THIS MAKES IT AVAILABLE AS AN ADVANCED BOOT OPTION IN THE LATER HALF OF STEP 1 FOR THE NEXT BOOT.

EASY WAY TO REMEMBER WINDOWS 2000 BOOT SEQUENCE:

1) POST
2) INITIAL STARTUP
3) BOOTSTRAP LOADER
4) OPERATING SYSTEM SELECTION
5) HARDWARE DETECTION
6) HARDWARE PROFILE SELECTION
7) WINDOWS 2000 KERNEL
8) LOGON

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