When these are tweaked correctly, performance can increase quite a bit. Set Optimal Bus speed settings. This point appears first because it's most important. The bus speed of the system directly affects how fast it is because it affects the communication lines between the parts. The processor speed relies on the bus speed.
Processor speed is the result of the bus speed times the multiplier.
A multiplier is the number of times faster the processor is than the bus. You want to use the fastest bus speed supported by your motherboard. In order to do this, you may need to lower the multiplier to relate to the CPU speed. This is controlled by jumper settings on the motherboard, or in SoftMenu if your board is jumperless. More on this subject in Overclocking .