What happened after the computer powers down

1. Press the power-on key. A wire connected to the power-on key will send a signal to the motherboard and request the power-on.

2. the motherboard receives this signal and forwards the signal to the power supply. The power supply starts to work.

3. After the Power Supply provides a stable voltage for each part of the motherboard, the "power_good" signal is sent to the BIOS.

4. After the BIOS receives the signal, start post (power on Self Test) to check whether the power supply is stable and whether the hardware devices (such as memory) are connected.

5. After the POST check is completed, the BIOSProgramLoad the tail address (such as 0xfffff0 or another address) to the memory, and then store a jump command at the 0x0 address of the memory to jump to the BIOS address in the memory.

6. The CPU executes commands at 0x0. This is a jump command, so it will jump to the BIOS program storage and start to execute the BIOS program.

7. BIOS sets IVT (interrupt vector table) at the beginning of the memory and stores some interrupt commands here. Then, check the computer hardware. Then, run the int 0x19 command to check the storage media in the specified order (for example, in the order of floppy disk, CD, and hard disk) and find the programs that can be started (bootable device in English ), load this program (bootloader) to 0x7c00 of the memory. Start executing the bootloader.

(Note: The Int 0x19 command is int 19 h. function: Reload the boot program)

Reprinted from: http://www.cnblogs.com/wangshuo/archive/2011/11/09/2242479.html