The frequency ratio setting controls the multiplier of the CPU’s external clock rate. As such, this setting can be used to effectively underclock or overclock the CPU.

Example: The CPU in Notebook-A has an external clock rate of 166.67 MHz. The frequency ratio (aka multiplier) of the CPU is x14.  166.67 * 14 = 2333.33 MHz (2.33 GHz). If the multiplier were set to x15 instead of x14, the new clock speed of the CPU would be 2500MHz (2.50GHz). The value obtained by multiplying the external clock by the frequency ratio is known as the internal clock of the CPU. In the previous example, the internal clock rate was 2.50GHz.

Unfortunately, this setting has no real effect in most computers (particularly laptops) as Intel usually locks the multipliers of its CPU’s with the PLL. Circumventing this usually requires a hardware modification.