The Multiplier is used in combination with the oscillator to increase the number of state changes from zero to one. The Multiplier is another oscillator circuit designed to increase the base system clock's output and simulate a much higher speed.
For instance, for a 1 gigahertz CPU chip, on a mainboard with a 200megahertz clock, you would need to set the multiplier to 5 to get the CPU up to the correct speed. On many mainboards, you must set voltages, clock speeds and multipliers to correctly configure a CPU to run correctly.
If this sounds complicated, it is. Just always remember to read the manual that came with your mainboard. Many mainboards today come with auto-detection capabilities to determine the CPU type and speed, and automatically configure the voltage, clock and multiplier settings (as well as clock speeds for memory and devices).