Boot sequence

On standard PC

Upon starting, a personal computer's CPU reads the instruction located at the memory register labelled FFFF0h of the BIOS ROM (Read only memory). This memory register location is at the end of system memory. This memory register contains a jump instruction that informs the CPU where the CPU can find the real BIOS start-up program.

The CPU of the computer executes the BIOS ROM code that contains the boot routine code. The BIOS executes the boot routine code and reads the master boot record. From the master boot record, the BIOS determines the active primary partition from which to boot an operating system. The active primary partition will contain a partition boot record that contains the instructions to boot the specific operating system. The BIOS passes this data to the CPU. The CPU executes the operating system boot instructions contained within the active primary partition.

This design allows the BIOS to load any operating system without knowing exactly where to start inside its partition.

Some other procesor have another kind of boot modes, most DSP include :

• Serial mode boot
• Parallel mode boot
• HPI boot
• Warm boot