Stands for "Central Processing Unit." The CPU is the primary component of a computer (Compared to Human anatomy it would be the brain) that processes instructions. It runs the operating system and applications, constantly receiving input from the user or active software programs. It processes the data and produces output, which may be stored by an application or displayed on the screen.

The CPU contains at least one processor, which is the actual chip inside the CPU that performs calculations. For many years, most CPU's only had one processor, but now it is common for a single CPU to have at least two processors or "processing cores." A CPU with two processing cores is called a dual-core CPU and models with four cores are called quad-core CPU's. High-end CPU's may have six (hexa-core) or even eight (octo-core) processors. A computer may also have more than one CPU, which each has multiple cores. For example, a server with two hexa-core CPU's has a total of 12 processors.

While processor architectures differ between models, each processor within a CPU typically has its own ALU (Arithmatic Logic Unit), FPU, register, and L1 cache. In some cases, individual processing cores may have their own L2 cache, though they can also share the same L2 cache. A single frontside bus routes data between the CPU and the system memory (RAM - Random Access Memory).

NOTE: The terms "CPU" and "processor" are often used interchangeably. Some technical diagrams even label individual processors as CPUs. While this verbiage is not incorrect, it is more accurate (and less confusing) to describe each processing unit as a CPU, while each processor within a CPU is a processing core.

Two of the most popular manufacturers for CPU's for home desktop's and gaming machines are AMD and Intel.



The performance or speed of a processor depends on, among many other factors, the clock rate (generally given in multiples of hertz, 2.4GHz 3.1.GHz etc.) and the instructions per clock which together are the factors for the instructions per second, that the CPU can perform. Due to specific capabilities of modern CPU's, such as hyper-threading and uncore, which involve sharing of actual CPU resources while aiming at increased utilization, monitoring performance levels and hardware utilization gradually became a more complex task. As a response, some CPU's implement additional hardware logic that monitors actual utilization of various parts of a CPU and provides various counters accessible to software; an example is Intel's Performance Counter Monitor Technology.


Overclocking is to run a Processor faster than the speed which for which it has been tested for and improved. It is away for users to get an extra boost without the addition (or cost) of new hardware. Overclocking is very popular amongst dedicated PC gamers.

The most common methods of overclocking your CPU is to either raise the multiplier or raise the FSB (frontside bus) — while not the only options they are the most common. To understand overclocking, you have to understand the basics of CPU speeds. The speed of a CPU is measured in Megahertz (MHz) or Gigahertz (GHz). This represents the number of clock cycles that can be performed per second. The more clock cycles your CPU can do, the faster it processes information.

The formula for processor speed is frontside bus x multiplier = processor speed.

(1) Pentium III 450MHz
The CPU runs at 450 million clock cycles per second. The CPU runs at a speed of 450 megahertz. Using the processor speed equation we have: 100MHz (frontside bus) x 4.5 (multiplier) = 450MHz (processor speed)

The frontside bus connects the CPU to the main memory on the motherboard — basically, it's the conduit used by your entire system to communicate with your CPU. One caution with raising the FSB is that is can affect other system components. When you change the multiplier on a CPU, it will change only the CPU speed. If you change the FSB you are changing the speed at which all components of your system communicate with the CPU.

Using the example above, the multiplier is 4.5. Since valid multipliers end in .0 or .5, you could try increasing the multiplier to 5.0 to obtain a performance boost (which would result in 100MHz x 5.0 = 500MHz). By far the easiest way to overclock a CPU is to raise the multiplier, but this cannot be done with all systems. The multiplier on newer Intel CPUs cannot be adjusted, leaving Intel overclockers with the FSB overclocking method (because of this AMD is becoming more of a popular choice for over clockers). The equation formula doesn't change for the method of raise the FSB. In the example above the FSB was 100MHz. Raising it to 133Mhz would change the equation (133Mhz x 4.5 = 598.5 MHz).

Overclocking Risks (and There Are Many)

Overclocking comes with many risks, such as overheating, so you should become familiar with all the pros and cons before you attempt it. Additionally, overclocking isn't supported by the major chip manufacturers which means overclocking your CPU will void your warranty. Overclocking can also decrease the lifespan of the CPU, cause failure in critical components and may even result in some data corruption. You may also notice an increase in unexplainable crashes and freezes.


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