What Is a CPU? The Brain of Your Computer

Just as the brain controls numerous bodily functions and processes sensory information, the central processing unit (CPU) processes instructions from a computer system’s operating system (OS), software applications, and other components.

The CPU, also known as the processor or microprocessor, is the brain of your computer and its single most crucial component. It ensures the system runs smoothly and efficiently. The right CPU can mean the difference between a speedy machine and a computer that chugs at basic tasks.

Read on to understand the nitty-gritty of processors and how to choose the best one for your needs.

The first commercially produced microprocessor, Intel 4004, was launched in 1971 and could process up to 60,000 instructions per second.

Today, a microprocessor can quickly process billions of instructions per second. CPU technology has evolved by leaps and bounds in the last five decades.

The Function of the CPU

The CPU is typically located on the motherboard, the heart of the computer, alongside other peripherals such as RAM and expansion cards.

You may have heard of concepts such as CPU cores, clock speed, and CPU cache. These all affect performance, and you should know how they work if you’re in the market for a new computer.

While CPU technology has evolved drastically, its core function remains the same—to execute instructions ranging from basic arithmetic to complex tasks and control other computer components.

Early Developments

The world’s first electronic computer was the Electronic Numeric Integrator and Computer (ENIAC). It became operational in 1945 and used more than 18,000 vacuum tubes for processing and memory.

These vacuum tubes consumed a lot of electricity, took up a lot of space, and were prone to malfunction. It wasn’t until 1958 that the first commercial transistorized computer, IBM 7070, was launched, and computers began to evolve into the powerhouses they are today.

Milestones in CPU Development

Transistors are the basic building blocks of a CPU and enable rapid data processing. All computer data is made of bits, which the computer keeps track of by rapidly switching circuits on and off.

Transistors and vacuum tubes control electric flow, but transistors are much smaller than bulky vacuum tubes. Many modern transistors are microscopic!

Today’s CPUs have between 500 million and two billion transistors, while high-end CPUs have between five and 10 billion transistors. The shift from vacuum tubes to transistors was a significant milestone in CPU development, making computers more powerful and portable.

Just compare the room-sized ENIAC to the device you’re reading this on now, and you’ll get a sense of how much CPUs have evolved over the years.

Introduction of Integrated Circuits

The development of integrated circuits in the early 1970s revolutionized processor technology, as it enabled the packing of thousands of transistors, diodes, and resistors onto micro-sized silicon chips.

The first commercially produced processor to use this technology was the Intel 4004 microprocessor, launched in 1971. Google “Intel 4004” — it looks like a golden bug with 16 legs, but it packed a powerful punch for its time.

Key Historical CPUs

The IBM System/360 (1965) is just as iconic as the Intel 4004. While it’s not a CPU (it used a Model 30 CPU), it’s worth talking about, as it revolutionized data processing and unified a family of mainframes under a single architecture.

It was highly modular and compatible, and such is the longevity of its software that it’s still used in some IBM mainframes today. Intel 8008, Intel 80386, Intel Pentium, and AMD Phenom are superstars in their own right.

The CPU has three major components: the control unit (CU), arithmetic logic unit (ALU), and registers.

• Control unit (CU): The CU controls the fetch-decode-execute instruction cycle; It fetches instructions from main memory and interprets them (with immense help from the ALU). It communicates with all input and output devices and manages all units of the computer system.
• Arithmetic logic unit (ALU): As the name suggests, the ALU executes arithmetic and logical instructions. It works on binary numbers and is like the nerd working in the background on a school project while the control unit takes all the credit!
• Registers: Registers are high-speed memory units within a CPU that enable temporary data and instruction storage for processing. They minimize off-chip data movement during processing and help modern CPUs maintain necessary throughput levels.

The control unit fetches data and instructions from the memory unit (RAM or ROM) and stores them in a register.

The decoder then decodes the instructions, and the ALU performs arithmetic or logical functions on the data. The registers store manipulated data during instruction decoding as well.

Once the ALU has processed the instructions, the CU stores them in the main memory (RAM or ROM) or supplies them to an output device. This whole process is called the fetch-encode-execute style.

CPU components benefit from high clock speeds, multi-core processors, and hyper-threading technology, all aspects of the CPU’s architecture.

Not everyone needs (or can afford) a computer with high-end technology, though — by understanding the significance of these technologies, you can purchase a system that meets your needs.

Clock Speed

Clock speed determines the speed at which a CPU core can process instructions. It is typically measured in gigahertz (GHz), though legacy systems may still use megahertz (MHz).

The higher the clock speed, the greater the number of instructions a CPU can process per second — factors such as the number of CPU cores and threads also impact CPU performance.

Cores and Threads

Modern CPUs have multiple processing units, called cores, and can execute multiple instructions simultaneously. Older single-core CPUs were limited to just one instruction at a time.

Hyper-threading technology further increases core performance by dividing CPU cores into virtual cores (one core can be divided into a maximum of two virtual cores). Threads are created by the host OS and managed by the scheduler.

We’ve touched upon the fetch-decode-execute cycle. Now, it’s time to understand each step in detail. We’ll also explore the Instruction set architecture (ISA) and pipelining and superscalar architecture to enhance your understanding of how CPUs work.

Fetch-Decode-Execute Cycle

The fetch-decode-execute cycle is called the instruction cycle, as each step is repeated for a new instruction. Whether you want to check your emails, watch a Netflix show, or play a video game, thousands of instructions are executed in this cycle to run a program.

1. During the fetch stage, the instruction to be processed is fetched from the main memory (RAM or ROM) and encoded in an instruction register.

2. The decoder interprets the encoded instruction during the decode stage. The goal is to read the instruction’s effective address from the main memory and fetch all required data.

3. During the execute stage, the ALU can read the decoded instruction and data from the register, perform necessary computations, and write the result back to the register. The result is then sent to either the memory unit or an output device.

The cycle will repeat for the next instruction. However, the execution of an instruction can also be interrupted (in case of a priority situation, for example).

In this case, the CPU will execute the new instruction and then return to the previous one. This is referred to as the repeat stage.

Instruction Set Architecture (ISA)

The Instruction Set Architecture (ISA) defines the support of a CPU for software and operating system (OS) operations—it acts as a bridge between a computer’s software and hardware components.

The ISA defines supported commands, instructions, data types, registers, virtual memory, addressing modes, memory consistency, and hardware for main memory management. x86 and ARM are some popular ISAs.

Pipelining and Superscalar Architecture

Pipelining and superscalar architectures are enhancements for faster processing.

The former allows multiple instructions to be executed simultaneously. The catch is they must be in separate pipeline stages — the four stages being fetch, decode, execute, and writeback.

The latter takes things one step further. It includes all the features of pipelining but allows these instructions to execute in the same pipeline stage.

Both approaches are beneficial; Pipelining processes instructions sequentially, which is fantastic when dealing with large quantities of the same type of instructions.

On the other hand, Superscalar architectures emphasize parallelism and are best suited to handling complex tasks, breaking them down into smaller tasks, and executing them in parallel.

There are four types of CPUs:

• Desktop CPUs
• Mobile CPUs
• Server CPUs
• Embedded CPUs

While most people have some knowledge of desktop CPUs, mobile CPUs are less understood. Let’s dive into the types of CPUs below.

Desktop CPUs

Despite the name, desktop CPUs are used in laptops and desktops. Since these devices are larger than smartphones, they don’t have size, heat, or energy efficiency constraints and are built for high-end performance.

Desktop CPUs have higher clock speeds, multiple cores, larger caches, and larger heatsinks and fans.

While some smartphones have CPUs that can almost match the performance features of desktop CPUs, desktop CPUs are generally miles ahead. Intel Core and AMD Ryzen processors are some of the most popular desktop CPUs on the market.

Mobile CPUs

Today’s mobile CPUs ​​also have multiple cores— most smartphones have at least two cores, with some having up to eight cores.

While mobile CPUs aren’t as powerful as desktop CPUs, they prioritize power efficiency and portability. They’re constrained by size and designed for passive cooling, as these devices lack room for fans.

Apple A-series (ARM-based processors) and Qualcomm Snapdragon processors are popular mobile CPUs.

Server CPUs

Server CPUs focus on parallel processing, reliability, and scalability and are used to run cloud services, data centers, and large-scale applications.

They’re similar to desktop CPUs but are optimized for server workloads, balancing performance and power efficiency.

In shared hosting, for example, multiple websites are hosted on the same server, and a desktop CPU won’t suffice.

Intel Xeon and AMD EPYC processors are good examples of server CPUs.

Embedded CPUs

Embedded CPUs prioritize low power, stability, and longevity and are used in specialized cases such as automobiles, industrial appliances, and Internet of Things (IoT) devices.

In cars, embedded CPUs can be used for features such as parking assistance, satellite radio, and adaptive cruise control.

Embedded CPUs have modest clock speeds, minimal cores, and passive cooling and are optimized for specific tasks.

Embedded CPUs include Raspberry Pi and NXP i.MX processors.

Clock speed, cache memory, thermal design power (TDP), and the fabrication process are crucial factors determining CPU performance. You can also add the number of CPU cores and threads to this list—in many cases, the more cores and threads, the better.

Clock Speed and Overclocking

Clock speed determines the speed at which a CPU can retrieve instructions and data from the memory unit and interpret them.

The higher the clock speed, the more clock cycles the processor can complete per second, which results in quicker instruction and data processing.

As the name suggests, overclocking refers to tweaking the settings of a CPU, such as CPU voltage, to increase its clock rate.

While overclocking increases performance and is beneficial in certain use cases, it can lead to system damage, large amounts of dissipated heat, and voided warranties.

Cache Memory

CPU cache reduces the number of times the control unit can access main memory, improving system performance.

There are three levels of CPU cache:

• L1: The L1 cache, or primary cache, is the smallest and fastest cache level, and each core has a unit.
• L2: The L2 cache has medium capacity and latency and can be shared between cores, though some CPUs have core-specific L2 caches.
• L3: The L3 cache is the largest and slowest and is shared between all CPU cores.

To upgrade your cache memory, you must upgrade your CPU.

Thermal Design Power (TDP)

Thermal design power (TDP), or thermal design point, is the maximum amount of heat that a computer’s cooling system can handle without damaging its components under normal operating conditions.

If you intend to overclock or overwork your system, it’s important to note this and implement a sturdy cooling solution, such as fans or liquid cooling.

Additionally, if you feel your system is heating up in normal working conditions, consider an additional cooling solution.

Fabrication Process

If you’re in the market for a new computer system, you may notice processor specifications similar to 7nm, 12nm, and 16nm.

These numbers refer to the node size of transistors within the processor; The smaller the node size, the better. A smaller-sized transistor translates to better performance and efficiency.

According to Moore’s Law, the number of transistors in an integrated circuit will double every two years. As transistors get even smaller, CPUs get more and more powerful.

Choosing the right CPU is tricky, as numerous options are available in each price bracket. Some may offer more CPU cores, while others may include a higher clock speed.

While hexa-core and octa-core processors offer scintillating performance, a dual-core processor with good clock speed may be all you need. The first step to choosing the right CPU is determining your performance needs.

Performance Needs

Before setting aside a budget, determine why you need a new laptop or desktop. If you need a computer for general use, a dual-core or octa-core processor with good clock speed should suffice.

On the other hand, a content creator or serious gamer may need a higher core count and clock speed — a CPU with eight or more cores and a high clock speed should meet their needs.

Once you’ve determined your performance needs, go to an eCommerce platform such as Amazon, set filters accordingly, and look at products that meet these criteria. This should help you decide on a budget.

Compatibility

If you’re building a desktop computer or upgrading an existing system, ensuring your new CPU is compatible with existing infrastructure is essential.

While buying a new CPU is cheaper than buying a new computer, getting one incompatible with your current hardware can force you to spend extra money upgrading other components.

For starters, the CPU must be compatible with your motherboard and should fit the socket on it. CPU and RAM compatibility is also a must — you need to purchase a CPU that can support the maximum speed for your RAM chip. Failure to do so will slow RAM down, affecting computer performance.

Future-Proofing

When building or upgrading a desktop, you must anticipate future requirements. Opting for the latest CPU that matches your performance needs and is within your budget should help future-proof your computer.

If you can afford to spend more, consider processors that slightly exceed your performance needs. Future software applications will likely be more resource-intensive, especially for applications such as video games and multimedia software.

Processors were once supersized, but after over five decades of miniaturization, we’re finally approaching their limits—the smallest processor chip in the world is 2nm and contains 50 billion transistors.

The race to achieve 1nm CPU chips is well and truly on, with IBM and Intel leading the way. We may see a 1nm CPU chip by 2027 based on current projections. Here are some other future trends you should keep an eye on.

Technological Trends

Advances in artificial intelligence (AI) and machine learning (ML) are likely to improve how efficiently CPUs can process tasks. Companies are also developing specialized AI chips to handle AI-related tasks, as AI models are complex and require significant computing power for training.

Quantum computing, too, could revolutionize CPU technology. Our current computers use bits, which can exist in one of two states: on or off. A quantum computer uses quantum bits, or qubits, which exist simultaneously in a superposition of both states.

This allows quantum computers to perform calculations exponentially faster than a typical computer, leading to a massive boost in processing power. However, we’re still quite a ways off from consumer-grade quantum computing.

Market Trends

As major manufacturers such as Intel, AMD, Apple, and Qualcomm vie to create the fastest and most efficient CPUs, powerful computers are becoming more accessible to the masses.

Today, high-powered CPUs are found in everything from automobiles to home appliances, and the low cost and increased availability of computing power mean that companies are experimenting with products that have never been seen before.

While it isn’t clear which company will be the first to develop the 1nm CPU, the market is bound to see enormous amounts of innovation thanks to its competition.

Sustainability

Thanks to advanced lithography techniques, modern CPUs are smaller than ever. However, this means more than just smaller, faster computers.

As devices’ power and material requirements decrease, so does their environmental impact.

Modern innovations, such as heterogeneous CPU/GPU and energy-efficient devices, reduce power consumption and support sustainability.

Almost every device you use, from your laptop to your television, has a CPU chip. We use these devices from the moment we wake up until we fall asleep.

While some chips are more powerful than others, each has the same goal — to make our lives easier. In many ways, CPUs are just as important as our brains; they’re the brains of these devices, after all!