CPU

The central processing unit (CPU) is the unit which performs most of the processing inside a computer. To control instructions and data flow to and from other parts of the computer, the CPU relies heavily on a chipset, which is a group of microchips located on the motherboard.

The CPU has two components:

• Control Unit: extracts instructions from memory and decodes and executes them
• Arithmetic Logic Unit (ALU): handles arithmetic and logical operations

To function properly, the CPU relies on the system clock, memory, secondary storage, and data and address buses.

This term is also known as a central processor, microprocessor or chip

Techopedia explains Central Processing Unit (CPU)

The CPU is the heart and brain of a computer. It receives data input, executes instructions, and processes information. It communicates with input/output (I/O) devices, which send and receive data to and from the CPU. Additionally, the CPU has an internal bus for communication with the internal cache memory, called the backside bus. The main bus for data transfer to and from the CPU, memory, chipset, and AGP socket is called the front-side bus.

The CPU contains internal memory units, which are called registers. These registers contain data, instructions, counters and addresses used in the ALU's information processing.

Some computers utilize two or more processors. These consist of separate physical CPUs located side by side on the same board or on separate boards. Each CPU has an independent interface, separate cache, and individual paths to the system front-side bus. Multiple processors are ideal for intensive parallel tasks requiring multitasking. Multicore CPUs are also common, in which a single chip contains multiple CPUs.

CPU Overview

The picture below is an example of what the top and bottom of an Intel Pentium 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.

As you can see in the above picture, the CPU chip is usually in the shape of a square or rectangle and has one notched corner to help place the chip properly into the CPU socket. On the bottom of the chip are hundreds of connector pins that plug into each of the corresponding holes in the socket. Today, most CPU's resemble the picture shown above. However, Intel and AMD have also experimented with slot processors that were much larger and slid into a slot on the motherboard. Also, over the years, there have been dozens of different 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.

The CPU was first 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 to the right.

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.

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 that was 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 is a list of the more common types of CPUs for home or business computers.

Note:

There are multiple versions for some of these CPU types.

AMD processors

K6-2 K6-III Athlon Duron Athlon XP

Sempron 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

4004 8080 8086 8087 8088 80286 (286) 80386 (386) 80486 (486)

Pentium Pentium w/ MMX Pentium Pro Pentium II Celeron 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

 How fast does a CPU transfer data?

As with any device that utilizes electrical signals, the data travels very 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 (type of metal in the wire) through which the signal is 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 process data and do many of the same things as a CPU, it lacks the ability to perform many of the functions required by typical operating systems and software.

Could a computer work without a CPU?

No. All computers require some type of CPU.