UEFI - The New Boot Operating System In Your Computer
LIU/Brooklyn System Architechture
Booting Method on Intel x86 Hardware: Bios POST
After loading into memory the BIOS sets the Program Counter using a JUMP command
BIOS scans memory from 0x0C0000 to 0x0F0000 on the 2 KiB boundary.
ROMs have a memory boundary of 0x55 0xAA followed by a byte that describes the number of 512 byte blocks that the expansion ROM sits at in real memory.
The execute jumps to the optional ROM which now controls the system until done when it returns to BIOS to continue scanning.
Finished with all this, the BIOS now calls INT 19h. This usually Jumps the PC to read from Head 0, Track 0 of Sector 1 of a disk.
The Bootstrap Loader is then loaded to bootstrap loader, installing it into memory location 0x0000:0x7C00.
The Loader readers the Master Boot Record.
The BIOS is a dumb device that does not process instructions from the boot sector. This is left to the bootstrap program.
From http://www.coreboot.org/data/lbdoc/lb-8.html