BIOS screen can alter memory bus clockspeed and internal bus clockspeed

clipped from www.proprofs.com External Clock This setting controls the clock speed of the memory bus on the motherboard, and is normally 50, 60, 66 or 75 MHz. The internal processor speed is the product of the external clock speed of the motherboard and the multiplier used by the processor. Multiplier Factor This setting controls the multiplier that is used to determine the internal clock speed of the processor relative to the external or motherboard clock speed. The usual values are 1.5X, 2X, 2.5X, 3X, 3.5X and so on. When the CPU Operating Speed parameter is set to a specific number, the External Clock parameter is computed by the BIOS and this setting is disabled. The above are the most common settings for any CPU. There can be other options other than the above based on the kind of processor and motherboard being used.