What is a CPU and what is it used for?


What is a CPU? And do I need a quad or dual-core processor? What about AMD, or Intel? Acronyms are the tech world’s favorite way of making interesting technology sound so confusing. When looking for a new PC or Laptop, the specifications will mention the type of CPU you can find in a shiny new device. Desperately, they almost always fail to tell you why it’s so important.

When faced with the decision between AMD and Intel, dual or quad-core, and i3 vs i7 or i5 vs i9, it can be hard to say what the difference is and why it matters. Knowing which one is best for you is difficult.Â

What is a CPU?

CPU The Core Processing Unit (CPU) is often referred to as the brain of the computer. Although the CPU makes only one of many processing units, it is one of the most important. This is the part of the computer that performs calculations, actions, and executes programs.

The CPU takes instructional input from the computer’s RAM, decodes and processes actions, before sending output. CPUs are in all kinds of devices from computers and laptops, to smartphones, tablets, and smart TVs. A small, usually square chip is placed onto the device’s motherboard and interacts with other hardware to operate your computer. If you want to dig deeper into computer mechanics, a good place to start is J. Clark Scott’s book But How Do It Know? (English).

How Does a CPU Work?

There have been many improvements over the years since CPUs first appeared. Nonetheless, the basic function of the CPU remains the same consisting of three steps; fetch, decode and execute.


Just as you would expect, fetch involves receiving instructions. Instructions are represented as a series of numbers and passed to the CPU from RAM. Each instruction is just one part of each operation, so the CPU needs to know which instruction will come next. The address of the current instruction is held by the program counter (PC). The PC and instructions are then placed into the Instruction Register (IR). The length of the PC is then added to refer to the address of the next instruction.

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Reading Passwords

After the instructions are fetched and stored in the IR, the CPU forwards the instructions to a circuit called an instruction decoder. It converts instructions into signals to be passed to other parts of the CPU for action.


In the final step, the decoded instructions are sent to the relevant part of the CPU for completion. The result is usually written to a CPU register, where it can be referenced with subsequent instructions. Think of it like a memory function on your calculator.

How many Cores?

In the early days of computing, a CPU would only have one core. This means that the CPU is limited to only one set of tasks. This is one reason why computing is often a relatively slow and time-consuming, but world-changing affair. After pushing single-core CPUs to their limits, manufacturers started looking for new ways to improve performance. This push for increased performance led to the creation of multi-core processors. By now you’re likely to hear terms thrown around like dual, quad, or even octo-core.

A dual core processor is really just two separate CPUs on a single chip. By increasing the number of cores, the CPU can handle multiple processes simultaneously. This has the desired effect of increasing performance and reducing processing time. Dual-core processors were soon replaced by quad-core processors with four CPUs, and even octa-core processors with eight. Add hyper-threading and your computers can perform tasks as if they had up to 16 cores.

Understanding the Specifications

Having knowledge of CPU operation along with different core brands and numbers is helpful. However, there are plenty of options out there even with the same high-level specs. There are a few other specs that can help you decide between CPUs when it’s time to buy.

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Mobile Vs. Desktop

Traditionally a computer was a large static electronic device powered by a constant supply of electricity. However, the shift to mobile and the rise of smartphones means that we basically carry our computers with us everywhere we go. The mobile processor is optimized for efficiency and power consumption so the device battery lasts as long as possible.

In their discretion, manufacturers have named their mobile and desktop processors the same thing but with different prefixes. This is even though their products are different. The mobile processor prefix has “U” for ultra-low power, “HQ” for high-performance graphics, and “HK” for overclockable high-performance graphics. The desktop prefix includes “K” for overclockability, and “T” for optimized power.

32 Or 64-Bit

The processor does not receive a constant stream of data. Instead, it receives data in smaller chunks known as “words”. The processor is limited by the number of bits in a word. When 32-bit processors were first designed, it seemed like a huge word size. Moore’s Law continued to apply, however, and suddenly computers could handle more than 4GB of RAM – leaving the door open for new 64-bit processors.

Thermal Energy Design

Thermal Power Design is a measure of the maximum power in Watts that your CPU will consume. While lower power consumption is obviously good for your electricity bill, it can have another surprising benefit – less heat.

CPU Socket Type

To make the computer fully functional, the CPU needs to be attached to other components via the motherboard. When choosing a CPU, you need to make sure that the CPU and motherboard socket types match.

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L2 / L3 cache

L2 and L3 caches are fast on-board memory for the CPU to use during processing. The more you have, the faster your CPU will perform.


Frequency refers to the operating speed of the processor. Before multi-core processors, frequency was the most important performance metric among CPUs. Although there are additional features, the specifications are still important to take into account. For example, a very fast dual-core CPU can outperform a slower quad-core CPU.

Brain Operation

The CPU is actually the brain of the computer. It performs all the tasks we normally associate with computing. Most of the other computer components are actually there to support the operation of the CPU. Improvements made in processor technology including hyper-threading and multiple cores played an important role in the Technical Revolution.

Being able to tell the difference between a dual-core Intel i7 and a quad-core AMD X4 860K will make decision-making times a lot easier. Not to mention potentially saving you money on expected hardware. However, while important, there are many other ways to upgrade your PC as well.