I am looking for the boot sequence for Linux OS (Intel P4 processor) In particular, where the BIOS finisies the POST and jumps to the predefined location where the bootloader code is executed. I believe while the BIOS is running the processor is configured in real mode. So when the bootloader code is executing, will the processor switch to protected mode?( i am not sure). If the processor runs the bootloader in real mode then it can see only 1MB of RAM. In this case if the linux image is greater than 1MB how can it uncompress the image? Could anyone give me some pointers about this execution ??