Updated: 03/10/2024 by Computer Hope
Illustration of a CPU.

Alternately called a processor, central processor, or microprocessor, the CPU (pronounced sea-pea-you) is the central processing unit of the computer. A computer's CPU handles all instructions it receives from hardware and software running on the computer. For example, the CPU processed the instructions to use a web browser to open and display this web page on your computer.


The CPU is often called the brain of the computer because many believe it thinks like a human brain. However, it's more appropriate to refer to software as the "brain" and the CPU as a very efficient calculator. A CPU is really good with numbers, but if it wasn't for software, it couldn't do anything more than calculate. For further human body part comparisons see: How does the computer relate to the human body?


Many new computer users may improperly call their computer and sometimes their monitor the CPU. When describing the computer or monitor, it's proper to refer to them as either the "computer" or "monitor" and not a CPU. The CPU is a chip inside the computer.

CPU overview

The picture below is an example of what the bottom and top of an AMD RYZEN processor may look. The processor is placed and secured into a compatible CPU socket found on the motherboard. Processors produce heat, so they are covered with a heat sink to keep them cool and running smoothly. To help transfer the heat between the CPU and the heat sink

Computer CPU (Central Processing Unit)

As seen in the picture above, the CPU chip is usually square with one notched corner to help make sure it's properly inserted into the CPU socket. On the bottom of the chip are hundreds of connector pins that correspond to the socket holes. Today, most CPU's resemble the picture shown above. However, Intel and AMD have also experimented with slot processors. They were much larger and slid into a slot on the motherboard. Also, over the years, there were several types of sockets on motherboards. Each socket only supports specific types of processors and each has its own pin layout.

What does the CPU do?

The CPU's main function is to take input from a peripheral (keyboard, mouse, printer, etc) or computer program, and interpret what it needs. The CPU then either outputs information to your monitor or performs the peripheral's requested task.

CPU history

Intel 4004 processor

The CPU was first invented and developed at Intel with the help of Ted Hoff and others in the early 1970s. The first processor released by Intel was the 4004 processor, shown in the picture.

Components of the CPU

In the CPU, there are two primary components.

  1. ALU (arithmetic logic unit) - performs mathematical, logical, and decision operations.
  2. CU (control unit) - directs all the processors operations.

Machine cycle

Over the history of computer processors, the speed (clock speed) and capabilities of the processor have dramatically improved. For example, the first microprocessor was the Intel 4004 released on November 15, 1971, and had 2,300 transistors and performed 60,000 operations per second. The Intel Pentium processor has 3,300,000 transistors and performs around 188,000,000 instructions per second.

Types of CPUs

In the past, computer processors used numbers to identify the processor and help identify faster processors. For example, the Intel 80486 (486) processor is faster than the 80386 (386) processor. After the introduction of the Intel Pentium processor (which would technically be the 80586), all computer processors started using names like Athlon, Duron, Pentium, and Celeron.

Today, in addition to the different names of computer processors, there are different architectures (32-bit and 64-bit), speeds, and capabilities. Below are the more common types of CPUs for home or business computers.


There are multiple versions for some CPU types.

AMD processors

Athlon XP
Athlon 64
Mobile Athlon 64
Athlon XP-M
Athlon 64 FX
Turion 64
Athlon 64 X2
Turion 64 X2
Phenom FX
Phenom X4
Phenom X3
Athlon 6-series
Athlon 4-series
Athlon X2
Phenom II
Athlon II
E2 series
A4 series
A6 series
A8 series
A10 series

Intel processors

80286 (286)
80386 (386)
80486 (486)
Pentium w/ MMX
Pentium Pro
Pentium II
Pentium III
Pentium M
Celeron M
Pentium 4
Mobile Pentium 4-M
Pentium D
Pentium Extreme Edition
Core Duo
Core 2 Duo
Core i3
Core i5
Core i7
Core i9

The AMD Opteron series and Intel Itanium and Xeon series are CPUs used in servers and high-end workstation computers.

Some mobile devices, like smartphones and tablets, use ARM CPUs. These CPUs are smaller in size, require less power, and generate less heat.

How fast does a CPU transfer data?

As with any device that utilizes electrical signals, the data travels near the speed of light, which is 299,792,458 m/s. How close to the speed of light a signal can get depends on the medium (metal in wire) through which it's traveling. Most electrical signals are traveling at about 75 to 90% the speed of light.

Could a GPU be used in place of a CPU?

No. Although GPU's can do many of the same things as a CPU, they lack the ability to perform functions required by some operating systems and software.

Could a computer work without a CPU?

No. All computers require some type of CPU.

Computer acronyms, Coprocessor, CPU socket, CPU terms, Dual-core, Hardware terms, Logic chip, Motherboard, Parallel processing, Processing, Register, Unit