What Is The CPU?

Date First Published: 30th June 2022

Topic: Computer Systems

Subtopic: Computer Hardware

Article Type: Computer Terms & Definitions

Difficulty Level: 4/10

Learn more about what the CPU is in this article.

Stands for Central Processing Unit. The CPU, also known as the processor, is a component of a computer that handles and processes the instructions that it receives from hardware and software. For example, every time an application is opened on a computer, the CPU has processed those instructions. Without the CPU, a computer would not be able to boot as it would be unable to process any instructions that it receives. Calculating, sorting, and searching take place in the CPU.

In a computer, the CPU is stored in the CPU socket on the motherboard.

Note:

The CPU is sometimes referred to as the ‘brain’ of the computer due to its role of handling and processing all the instructions of the computer.

CPU Components

Key components of the CPU include:

• Control unit - This controls and monitors the input and output of data in the system and translates input information that it receives into control signals, which are then sent to the CPU. The control unit checks that the signals have been successfully delivered and that data goes to the appropriate place at the correct time. It does not carry out any data processing operations.
• Immediate access store - This stores all the data and programs that the user is currently working with. (e.g. typed numbers are stored inside a calculator whilst it processes the calculations).
• Arithmetic and logic unit - The part of the CPU that performs arithmetic and logic operations. It is the last component to perform calculations in the processor and carries out mathematical as well as bitwise operations on binary numbers. Each task that a computer accomplishes is completed there. For example, the arithmetic and logic unit is used in word processors to calculate the pixels on the screen that should change so that the typed characters can be seen.
• Register - A temporary storage area in the CPU that stores small amounts of data needed during processing, such as the address of the next instruction to be performed.

The arithmetic and logic unit is divided into two parts, which include:

• The arithmetic part that handles calculations, such as 5 + 8 = 13.
• The logical part that handles logical comparisons, such as 7>3.

CPU Operations

The CPU usually runs programs using the fetch-decode-execute cycle. As soon as a computer is turned on, this cycle begins. The three steps of the cycle include:

• Fetch - Instructions are received from the RAM of a computer.
• Decode - Allows the CPU to identify the instruction that needs to take place so that it can determine how many operands it needs to fetch to perform the instruction.
• Execute - Where the operation is performed. Every necessary part of the CPU is activated to perform the instructions.

CPU Speed

The CPU speed is based on three factors, which include:

• Clock speed
• Cores
• Cache

Clock speed

The CPU is measured in clock speed. This refers to the speed the CPU can handle instructions. The clock speed is measured in cycles per second and one cycle per second is equivalent to 1 hertz (Hz), meaning that a CPU with a clock speed of 3 gigahertz (GHz) is capable of handling three billion cycles per second.

In the 1980s, processors often ran between 3-5 MHz, equal to 3-5 million pulses per second. As of now, processors run much, much faster.

Even though it seems like the CPU can handle and process multiple instructions at the same time due to the speed it can carry them out, it can only carry out one instruction at a time.

Cores

The cores of the CPU can be known as the ‘brains’ of them. Every CPU core can separately carry out operations from the others and they have a significant effect on the speed of a computer. A CPU with two cores is known as a dual-core processor, four cores: quad-core processor, six cores: hexa-core, and eight cores: octa-core.

The more cores a CPU contains, the more instructions that can be processed and handled at the same time. For example, a dual-core processor can carry out two instructions in the same period of time that it takes for a single-core processor to carry out one instruction.

However, processors with more than one core have a number of disadvantages, which include:

• They are more expensive to make and design.
• They use more power than a single-core processor.
• Because the instructions have to be split between the cores to decide which one will carry them out, it will slow the processor down. This is because the results have to be merged together at the end.

Cache

The CPU will often store commonly used instructions and data in the cache in order to increase the speed of retrieving data from the memory of the computer. It allows information to be accessed more quickly than if it was accessed from the hard drive.

Before requesting data from the RAM, the CPU control unit automatically checks the cache for instructions, eliminating the need to constantly fetch instructions and data from the RAM.

Difference Between CPU and GPU

The terms ‘CPU’ and ‘GPU’ look similar, but they are two different processing units. The role of the GPU (Graphics Processing Unit) is to handle and process graphics operations, such as 2D and 3D calculations.

History

The term ‘central processing unit’ has been around since 1955. Early computers, such as the ENIAC had to be physically rewired to perform different tasks, causing these computers to be called ‘fixed-program computers’. The earliest devices that had CPUs were stored-program computers.

The design of J. Presper Eckert and John William Mauchly's ENIAC already included the concept of a stored-program computer, but it was originally left out so that it could be completed more quickly. Mathematician John von Neumann published a paper titled First Draft of a Report on the EDVAC on June 30, 1945, before ENIAC was created. It was the general design of a stored-program computer, which would be completed in August 1949. EDVAC was created to carry out a specific amount of operations of different kinds.

Additionally, the programs that were created for the EDVAC were designed to be stored in fast computer memory rather than being limited by the physical hardware of the computer.

Early CPUs were custom designs and were a component of larger, occasionally recognisable computers. However, the introduction of multi-purpose processors produced in large quantities has essentially replaced this method of creating unique CPUs for a certain purpose.

With the rise in popularity of integrated circuits, this standardisation that started with mainframes and minicomputers with single transistors has progressed quickly (IC). The IC has made it possible to design and produce increasingly complex CPUs with tolerances on the order of nanometers. Beyond the restricted use of specialised personal computers, the development and standardisation of CPUs have extended the presence of digital gadgets in modern-day life. Modern microprocessors can be found in a variety of electronic devices, such as cars, mobile phones, and occasionally, even in toys.

The first CPU was introduced in 1971 by Intel, called Intel 4004. It was a 4-bit CPU with a speed of 740 KHz. Five months later, Intel 8008 was introduced. It was the first 8-bit microprocessor.