The Central Processing Unit

Central Processing Unit

Is considered the brain of the computer. It is sometimes referred to as the processor. Most calculations take place in the CPU. In terms of computing power, the CPU is the most important element of a computer system. CPUs come in different form factors, each style requiring a particular slot or socket on the motherboard. Common CPU manufacturers include Intel and AMD.

MMX

MMX is a set of multimedia instructions built into Intel processors. MMX enabled microprocessors can handle many common multimedia operations that are normally handled by a separate sound or video card. However, only software specifically written to call MMX instructions can use the MMX instruction set.

Overclocking

Overclocking is a technique used to make a processor work at a faster speed than its original specification. The opposite of overclocking is CPU throttling. CPU throttling is a technique used when the processor runs at less than the rated speed to conserve power or produce less heat. Throttling is commonly used on laptops and other mobile devices.

Examples of CPU Types

Single Core CPU - One core inside a single CPU that handles all of the processing capability. A Dual Core CPU - Two cores inside a single CPU in which both cores can process information at the same time. A Triple Core CPU - Three cores inside a single CPU that is actually a quad-core processor with one of the cores disabled. A Quad Core CPU - Four cores inside a single CPU in which all cores can process information simultaneously for enhanced software applications.

Hyperthreading

Some CPUs incorporate hyperthreading to enhance the performance of the CPU. With hyperthreading, the CPU has multiple pieces of code being executed simultaneously on each pipeline. To an operating system, a single CPU with hyperthreading performs as though there are two CPUs.

CPU Operation

The CPU executes a program, which is a sequence of stored instructions. Each model of processor has an instruction set, which it executes. The CPU executes the program by processing each piece of data as directed by the program and the instruction set. While the CPU is executing one step of the program, the remaining instructions and the data are stored nearby in a special memory called cache. There are two major CPU architectures related to instruction sets.

CPU Socket

The CPU socket or slot is the connector that interfaces between the motherboard and the processor. Most CPU sockets and processors in use today are built around the pin grid array (PGA) architecture, in which the pins on the underside of the processor are inserted into the socket, usually with zero insertion force (ZIF). ZIF refers to the amount of force needed to install a CPU into the motherboard socket or slot. Slot-based processors are cartridge-shaped and fit into a slot that looks similar to an expansion slot. Figure 1 lists common CPU socket specifications.

CPU Speed and Power

The power of a CPU is measured by the speed and the amount of data that it can process. The speed of a CPU is rated in cycles per second. The speed of current CPUs is measured in millions of cycles per second, called megahertz (MHz), or billions of cycles per second, called gigahertz (GHz). The amount of data that a CPU can process at one time depends on the size of the processor data bus. This is also called the CPU bus or the front side bus (FSB). The wider the processor data bus width, the more powerful the processor is. Current processors have a 32-bit or a 64-bit processor data bus.