BOOTING in WINDOWS XP. BY Justin Metzger. Power Good. Power Good is the signal sent to the processor from the power supply It is sent once the voltages ad current levels are acceptable This process takes anywhere form .1 to .5 seconds
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BOOTING in WINDOWS XP BY Justin Metzger
Power Good • Power Good is the signal sent to the processor from the power supply • It is sent once the voltages ad current levels are acceptable • This process takes anywhere form .1 to .5 seconds • Upon arrival of Power Good, the Timer Chip stops sending reset signals so the CPU can start operations
ROM BIOS code • The CPU starts executing the ROM BIOS code • The CPU loads the ROM BIOS starting at ROM memory address FFFF:0000 which is only 16 bytes from the top of ROM memory • The ROM BIOS does a test of central hardware to verify basic functionality • Any errors that happen now will be reported by means of ‘beep-codes’
Cold Start or Warm Start • To determine whether this is a warm start or a cold start the ROM BIOS startup routines check the value of 2 bytes located at memory location 0000:0472 • Any other value other than 1234h indicates that this is a cold start • If this is a cold start the ROM BIOS executes a full POST • If this test is a warm start the memory test portion of the POST is switched off.
Difference between cold and warm start • Cold boot (cold start) is starting the computer after it has been powered down for a while • Warm boot (warm start) is restarting a computer that has already been turned on • For example in hibernating mode
What is POST? • POST is broken down into 3 components which are the following: • The video test initializes the video adapter, tests the video card and video memory, and displays configuration information or any errors • The BIOS identification displays the BIOS version, manufacturer, and date • The Memory Test tests the memory chips and displays a running sum of installed memory
CMOS • CMOS stands for Complimentary Metal Oxide Semiconductor • The BIOS locates and reads the configuration information stored in CMOS • CMOS is maintained by the current of a small battery attached to the motherboard • CMOS is a small area of memory containing 64 Bytes • Most importantly for the ROM BIOS startup routines CMOS indicates the order in which drives should be examined for an operating system-floppy, CD ROM, or fixed disk
Finally Logging on • The Window XP booting process is not complete until a user has logged on • The process is begun by the WINLOGON.EXE file • Which is loaded as a service by the kernel and continued by the Local Security Authority, which displays the logon dialog box • The logon dialog box appears at approximately the time that the Services Subsystem starts the network service