What is CPU? Parts and Functions of a CPU

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What is CPU? – Overview

The CPU (central processing unit) is often regarded as the brain of a computer. It’s one of the many processing units but arguably the most vital.

Inside a computer, the CPU is in charge of actions, calculations and running programs.

In older PCs, these functions were split between various processors. However, recent design and production improvements mean that a whole CPU can fit onto a single chip.

For this reason, you’ll hear CPUs called microprocessors as well. 

These smaller sizes mean we can reduce PC sizes allowing us to have sleeker and lighter laptops.

CPUs are also present in smartphones and tablets, and they take care of performance there as well. Let’s look at the functions, parts and specs of a CPU in detail. 

What Are the Functions of The CPU?

What Is CPU?

What Is CPU? – What Are the Functions of The CPU?


As you might expect, fetching involves getting instructions. The instruction is represented by a series of digits and is conveyed to the CPU by the RAM.

Each instruction is a small fragment of any operation, so the CPU needs to know what’s next.

The present instruction address is held by a PC (program counter). The instructions and PC are placed inside an IR (instruction register).

Then the program counter length is increased to reference the succeeding instruction’s address.


Once the instruction is fetched and deposited in the instruction register, the CPU forwards the instruction to a circuit known as the ID (instruction decoder).

This transforms the instruction into signals to be ferried through other CPU parts for processing. 


The decoded instructions are ferried to the relevant CPU parts to be completed. The results are typically recorded on a CPU register where later instructions can reference them.

A real-world example of this is the memory function on a calculator. 


The result of the execution is taken back to the memory and stored for later retrieval if and when needed. This is also referred to as writing to memory. 

What Are the Main Parts of A CPU?

What Is CPU?

What Is CPU? – What Are the Main Parts of A CPU?

CU (Control Unit)

This portion of a CPU regulates the flow of input and output. It’s the part that fetches and retrieves instructions from the main memory and decodes them.

ALU (Arithmetic Logic Unit)

This is the portion of the CPU in charge of processing. Its where all the arithmetic calculations are done, such as addition, subtraction, division and multiplication.

It’s also in charge of logical operations, such as data comparison, necessary for decision-making. 


This is a fast memory location; the instructions currently being produced during the fetch-execute succession are stored here for quick access by the CPU. 

Understanding CPU Specs

To help you compare various CPU models, take a look at the specifications below. They will help you decide between multiple CPUs to find one that best suits your needs. 

32 vs. 64-bit CPUs

What Is CPU?

What Is CPU? – 32 vs. 64-bit CPUs

A CPU doesn’t get a continuous flow of info. Instead, it receives the info in smaller fragments known as words. The performance of a CPU is restricted by the number of bits in a word.

Although 32-bit CPUs were first introduced in the 1940s, they didn’t become useful until several decades later.

By the 90s, they were affordable enough to be used in consumer electronics. At this point, everyone thought that 32-bit CPUs were future-proof.

However, with tech advancements, 32-bit CPUs became a limiting factor for both software and hardware.

So they were replaced by 64-bit CPUs, which are the current global standard. This means you’re better off with a PC powered by a 64-bit chip.


Frequency refers to the processing speed of a CPU. Prior to multi-core CPUs, frequency was the most vital performance metric between individual processors. 

Despite new CPU features, frequency is still a critical spec to take into account. For instance, a super-fast dual-core CPU will dwarf a slower quad-core CPU. 

L2 and L3 Cache

What Is CPU?

What Is CPU? – L2 and L3 Cache

L2 and L3 cache is fast on-board memory used by the CPU during processing. The more L2 and L3 cache on a CPU, the faster it performs.

Socket Type 

A CPU needs to be connected to other components via the motherboard for a computer to work. When buying a CPU, ensure the CPU and motherboard socket types are the same.

TPD (Thermal Power Design)

TDP is a measure of max CPU power consumption in watts. While lower power consumption is suitable for your power bills, it also has another added benefit; less heat. 

Final Thought

To sum it all up, CPUs make PCs, smartphones, tablets and other connected devices more powerful and ultimately more valuable.

But there are plenty of changes you can make to your existing system to help boost and revolutionize its performance. 

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