The clock speed that the component is rated for is at or below the speed at which the CPU has passed the manufacturer’s functionality tests when operating in worst-case conditions (for example, the highest allowed temperature and lowest allowed supply voltage)

overclocking is the process of running a computer component at a higher clock rate than it was designed for or was specified by the manufacturer.

Overclocking a computer’s processor or memory causes it to go faster than its factory rated speed. A processor rated at 2.4GHz might be overclocked to 2.5GHz or 2.6GHz, while memory rated at 200MHz might be pushed to 220MHz or higher. The extra speed results in more work being done by the processor and/or memory in a given time period, increasing the overall computing performance of the PC.

The most obvious reason to overclock a computer system is to squeeze some additional performance out of it at little or no cost. Overclocking the processor and system memory can significantly boost game performance, benchmark scores and even simple desktop tasks. Since almost every modern processor and memory module is overclockable to at least a slight degree, there are few reasons not to attempt it.

most important considerations for overclocking :

Heat :

The faster a computer goes, the more heat it produces. This is especially true when the voltage being fed to certain components is increased, a standard overclocking method. Excess heat in the processor, motherboard chipset or memory can cause crashes and system instability, and may be one of the limiting factors in determining the maximum overclock for a system so we need more cooling when overclocking

Power Supply :

Overclocking a computer system also increases the amount of power it draws, and this may lead to system instability if its old 300Watt power supply is not up to the task. If overclocking a modern Pentium 4 or Athlon 64 system, plan on upgrading the power supply to at least 400Watts

clock rate ” Clock speeds  “ is the speed at which a microprocessor executes instructions. every computer contains an electronic clock, which produces a sequence of regular electrical pulses used by the control unit to synchronize the components of the computer and regulate the fetch-execute cycle by which program instructions are processed that regulates the rate at which instructions are executed and synchronizes all the various computer components. The CPU requires a fixed number of clock ticks (or clock cycles) to execute each instruction. The faster the clock, the more instructions the CPU can execute per second.

in other word ,  clock rate is the fundamental rate in cycles per second at which a computer performs its most basic operations such as adding two numbers or transferring a value from one processor register to another. it is the frequency of the clock in any synchronous circuit.

Clock speeds are expressed in megahertz – millions of pulses a second – (MHz)  or gigahertz (GHz).