the present invention relates to a method for loading a central processing unit microcode into a basic input / output system and a method for updating the central processing unit microcode of the basic input / output system . a system management interrupt instruction is applied to inform the basic input / output system an address and a length of the central processing unit microcode . then , the basic input / output system performs an interrupt instruction to load the central processing unit microcode to a specific block of the basic input / output system .