A method for overclocking a central processing unit (CPU) of a computer motherboard is disclosed. Step A is to set a second frequency of front side bus (FSB) by an operating interface of BIOS. Step B is to determine FSB frequency Fn at each of N stages according to a difference between a first frequency and the second frequency. Step C is to load the CPU with an operating system by booting the CPU at the first frequency of FSB, and send an interruption signal to the CPU from a chipset at predetermined intervals upon completion of the loading of the operating system so as to allow the BIOS to gain control over the CPU, and execute step D by the CPU on each of N occasions of interruption until the FSB frequency of the CPU is changed to the second frequency. Step D is to execute the BIOS by the CPU on the nth occasion of interruption such that the CPU operates at the FSB frequency Fn, and allow the operating system to resume control over the CPU.