What Is a CPU (Processor)? Definition, Functions & How It Works Explained

A CPU (Central Processing Unit) is the main working component of a computer that performs the arithmetic and logical operations specified by a program, controls the computing process, and coordinates the work of all computer devices. In short, the CPU is the "brain" of the computer. The first microprocessor, the Intel 4004 (the world's first commercially available single-chip CPU), was created in 1971 under the direction of Dr. Ted Hoff at Intel for microcalculators and was custom-built for a Japanese firm. This begs the question: What is a CPU?

In addition to the CPU, there are specialized microprocessors — chips for processing graphics, 3D sound, compression and decompression, which are placed on specialized, additional boards. On the CPU chip are:

• The processor proper, the main computing device, which consists of millions of logic elements — transistors.
• The coprocessor is a special unit for floating point (or comma) operations. It is used for particularly accurate and difficult calculations, as well as for working with a number of graphics programs.
• First-level cache memory — ultrafast memory designed to store intermediate results of calculations.
• The second level cache memory is slower but larger in size — from 128 to 512 kbytes. The area of the processor is 4 to 6 square centimeters.

Processor characteristics

The main CPU characteristics are clock frequency, manufacturing technology, system bus frequency, and form factor. Together these four parameters define how fast a processor works and how it physically connects to the computer.

Processor clock frequency. The processor clock frequency, measured in megahertz (MHz) or gigahertz (GHz), indicates how many instructions the processor is capable of executing per second — the higher the clock frequency, the faster the CPU works. The clock speed is indicated by the number in the processor name (e.g., the Intel Pentium 4 2400 MHz, a Pentium 4 processor clocked at 2400 MHz or 2.4 GHz).

Processor manufacturing technology. The manufacturing technology is determined by the size of the minimum elements of the processor. The production technology of modern processors, for example, the AMD Athlon XP (a desktop CPU based on the Thoroughbred core), is 0.13 µm.

System bus frequency. The system bus frequency is directly related to the frequency of the processor itself through a "multiplication factor". The processor frequency is the system bus frequency multiplied by the processor by some inherent value. For example, a processor frequency of 1700 MHz is the system bus frequency of 100 MHz multiplied by a factor of 17.

Processor Form Factor. Processor form factor is the type of processor manufacturing, its design and the way it is connected to the motherboard.

• Square-shaped processors (socket type) — a case with legs-pins.
• There is a form slot (slot) — legs-pins are placed on one side of the processor board.
• Old models of processors had Socket7 form factor (AMD processors — K6, K6-2, K6-2+, K6-3, Intel — Pentium II (200 - 266), Cyrix (M2), Centaur Technology (IDT)).
• Processors with Slot1 form factor are Intel processors: Pentium II (233-600 MHz), Pentium III (Katmai) and Celeron (300-400 MHz).
• Socket A processors are AMD processors: Athlon (Thunderbird, Palomino, Thoroughbred), Duron.
• Socket370 processors are Intel processors: Pentium III (Coppermine), Celeron (Mendocino, Coppermine-128, Tualatin-128).
• Socket-423 form-factor processors — Pentium IV (Willamette), Socket 478 — Pentium IV (Willamette, Northwood).

We hope that now, to the question "What is a processor?", you will be able to give a comprehensive answer. To learn more about how computer components work together with applications, see our overview of the concept of software, or browse more articles in our PC section.