What is a CPU?

A central processing unit (CPU) is a hardware component that’s the core computational unit in a server. Servers and other smart devices convert data into digital signals and perform mathematical operations on them. The CPU is the primary component that processes the signals and makes computing possible. It acts as the brain of any computing device. It fetches instructions from memory, performs the required tasks, and sends output back to memory. It handles all computing tasks required for running the operating system and applications.

How did CPU technology advance over time?

The earliest computers used vacuum tubes for processing. Machines like the ENIAC and UNIVAC were large and bulky, and they consumed a lot of power and generated significant heat. The invention of transistors in the late 1940s revolutionized CPU technology. Transistors replaced vacuum tubes, making computers smaller, more reliable, and more energy-efficient. In the mid-1960s, integrated circuits (ICs) were developed, which combined multiple transistors and other components on a single computer chip. CPUs became even smaller and faster, leading to the emergence of microprocessors.

Read about computer chips »


Microprocessors combined the entire CPU on a single IC chip, which made computers more accessible and led to the development of personal computers. Initially, CPUs could handle 16 to 32 bits of data at a time. In the early 2000s, 64-bit CPUs emerged, which allowed for larger memory addressing and supported more extensive data processing.

As transistor density increased, it became challenging to boost single-core CPU performance further. Instead, CPU manufacturers began using multi-core processor architectures to integrate multiple cores onto a single chip.

Modern-day processors

With the rise of mobile devices, power efficiency has become crucial. CPU manufacturers now develop low-power and energy-efficient CPUs for modern portable devices like smartphones and tablets.

As artificial intelligence (AI) and graphics-intensive tasks became more prevalent, specialized CPUs like graphics processing units (GPUs) and AI accelerators are now used to handle the workloads.

Continued research and development in nanotechnology and materials science has paved the way for microscopic transistors and more powerful CPUs. Quantum computing and other emerging technologies hold the potential to further develop computer processor technology.

What are the components of a CPU?

A CPU is a complex electronic circuit that comprises several key components that process data and run instructions. The main components of a CPU are given next.

Control unit

The control unit manages instruction processing and coordinates data flow within the CPU and between other computer components. It has an instruction decoder component that interprets the instructions fetched from memory and converts them into micro-operations that the CPU can run. The control unit directs other CPU components to perform required operations.


Registers are small, high-speed memory storage locations within the CPU. They hold data that the CPU is currently working on and facilitate quick access to data. CPUs have several types of registers, like these:

  • General-purpose registers that hold operational data
  • Instruction registers that hold the current instruction being processed
  • A program counter that holds the memory address of the next instruction to be fetched

Registers provide faster access times than other memory levels like RAM or cache memory.


The arithmetic logic unit (ALU) performs basic arithmetic operations (addition, subtraction, multiplication, and division) and logical operations (AND, OR, and NOT) on data. It receives data from registers within the CPU, processes it based on the instructions from the control unit, and produces the result.

Memory management unit

Depending on the CPU architecture, there might be a separate bus interface unit or memory management unit. These components handle memory-related tasks, such as managing the CPU and RAM interaction. It also handles cache memory—a small and fast memory unit located within the CPU—and virtual memory that the CPU requires for data processing.


The CPU relies on a clock signal to synchronize its internal operations. The clock generates a steady pulse at a specific frequency, and these clock cycles coordinate the CPU's operations. The clock speed is measured in hertz (Hz) and determines how many instructions the CPU can execute per second. Modern CPUs have variable clock speeds, which adjust based on workload to balance performance and power consumption.

How does a CPU work?

Computer processors work with other hardware components and software programs to process data and manage the flow of information within electronic devices. They typically work in cycles, with each instruction cycle representing three main steps.

Core processor cycle

The basic steps in an instruction cycle are given next.

Instruction fetch

The CPU fetches instructions from memory. The instructions are binary codes representing specific tasks or operations for the CPU. The control unit interprets the instruction and determines the operation to be performed. It also identifies the specific CPU components required for the task.

Instruction processing

The CPU carries out the specified operation on the fetched data. It performs mathematical calculations, logical comparisons, data manipulation, or data transfer between registers or memory locations.

Result storage

After it executes instructions, the CPU may need to store the results in memory or update specific registers with the new data. The program counter (PC) is updated to point to the address of the next instruction to be fetched. The CPU repeats the cycle and fetches, decodes, and executes instructions sequentially.

Additional processor functions

The CPU can also handle control flow instructions like jumps and branches along with interrupts, signals generated by external devices, or events requiring immediate attention. When an interrupt occurs, the CPU temporarily suspends the current task, saves its state, and jumps to an interrupt service routine. After it processes the interrupt, the CPU resumes the previous task.

Modern CPUs often use techniques like parallelism and instruction pipelining to enhance performance. Multiple instructions can be in different cycle stages simultaneously, which allows for more efficient use of CPU resources.

What are some advanced CPU features?

The best CPU excels in performance, efficiency, and flexibility, allowing it to effectively handle a wide range of computing tasks. We give some advanced features next.


While a single-core processor was standard in the past, all CPUs have multiple physical cores today. A core is an individual processing unit within a CPU. More cores allow the CPU to handle multiple threads (sequences of instructions) in parallel, significantly improving overall performance. Applications can take advantage of the multi-core design by dividing tasks into smaller subtasks that can be completed simultaneously.


Hyper-threading is a simultaneous multithreading implementation developed by Intel that allows each CPU core to run multiple threads simultaneously. It allows each physical core to appear as two virtual cores in the operating system. The software uses available hardware resources more efficiently.

Advanced instruction sets

Modern CPUs also feature advanced instruction sets and technologies designed to accelerate specific tasks. These instruction sets go beyond the fundamental arithmetic and logical operations, providing additional capabilities to handle complex computations more efficiently.

For example, CPUs may include instruction sets specifically for these tasks:

  • Multimedia tasks, such as video decoding, audio encoding, and image processing.
  • Encryption and decryption algorithms, like Advanced Encryption Standard (AES) and Secure Hash Algorithm (SHA).
  • Single instruction, multiple data (SIMD) tasks that require the CPU to simultaneously perform the same operation on large datasets. These are tasks like graphics rendering, scientific simulations, and digital signal processing.
  • Virtualization, allowing virtual machines (VMs) to run more efficiently.
  • AI workloads like neural network operations.

How can AWS support your processor requirements?

Amazon Web Services (AWS) has offerings to support your processor requirements.

Amazon Elastic Compute Cloud (Amazon EC2) offers the broadest and deepest compute platform. It boasts more than 600 instances and a choice of the latest processor, storage, networking, operating system, and purchase model to help you best match your workload's needs. We are the first major cloud provider that supports Intel, AMD, and Arm processors, as well as the only cloud with on-demand EC2 Mac instances.

When you use Amazon EC2, you get these benefits right away:

  • Get the best price performance for machine learning training and the lowest cost-per-inference instances in the cloud
  • Choose the best mix of CPU, memory, storage, and networking resources for your applications
  • Select a preconfigured, templated Amazon Machine Image (AMI) to get up and running immediately

Get started with custom instances and processors on AWS by creating an account today.

Next Steps on AWS

Check out additional product-related resources
Check out Compute Services 
Sign up for a free account

Instant get access to the AWS Free Tier.

Sign up 
Start building in the console

Get started building in the AWS management console.

Sign in