Hello Osial,
This is an interesting question.
Perhaps to make it more clear, can you elaborate a little on the reason behind the question?
What is your objective? What do you expect to achieve by changing this?
Does your question involve any specific product (motherboard model, BIOS version)?
PS: Bear in mind that some BIOS changes could be platform-specific therefore it will be very important to know exactly what type of system you are referring to, or at least provide some examples on the matter.