The CPU works on two frequencies: An internal and an external.
The external clock frequency (the bus frequency) is the speed between the CPU and RAM. In the Pentium CPU’s it is actually the speed between L1 and L2 cache. In the Pentium II it is the speed between L2 cache and RAM.
-The internal clock frequency is the speed inside the CPU, that is between L1 cache and the various CPU registers.
Since clock doubling and bus speed can be freely adjusted on the motherboard according to your desires, you can in principle make the CPU run at 300 MHz.
You set the bus to 75 MHz and the clock factor to 4. Then the CPU runs at 300 MHz – if it runs. The question is whether the chip will tolerate that – if it will give a stable performance, since clock doubling means more than added heat.
We have now seen that there are two frequencies which can be manipulated, if you want to re-clock the CPU: The bus frequency can be increased, let’s say from 66 to 75 MHz. The CPU frequency can be increased.
That can happen as a result of an increased bus speed, which also affects the CPU frequency, or it can happen by using a greater clock factor. Or it can happen through a combination of both techniques.
Both techniques result in a faster PC. If the bus frequency is increased, it affects all data transport to and from RAM. It will work faster, to the joy of all work done on the PC. When the CPU internal frequency is increased, many applications will be happily affected.
The main disadvantage of over-clocking is your CPU will get heat and becomes hot which tends to break working circuit.
Source: http://www.techbusy.org/
