What's inside a computer?
The Processor or CPU (Central Process Unit) is the computer’s brain. It is really just a microprocessor chip. This microprocessor performs all calculations and controls all other components.
The microprocessor’s internal clock speed is measured in megahertz (MHz) or gigahertz (1 GHz = 1000 MHz). Another speed to be taken into account is the rate at which the motherboard and microprocessor communicate. This is known as external or bus speed, and is well below clock speed.
Real system operation speed depends not only on internal processor speed, but is also influenced by the speed of the external bus and other components.