At the core of every computer system lies the central processing unit (CPU), which acts as the brain of the device, executing instructions and performing calculations.
These CPUs are designed based on different architectures, each with its own unique characteristics, strengths, and capabilities.
In this comprehensive article, we’ll delve into the three most prominent CPU architectures: x86, x64, and ARM, and understand their differences, strengths, and the roles they play in the modern computing landscape.
What is a CPU and Instruction Set?
A CPU, or central processing unit, is the electronic circuitry that executes instructions and performs calculations within a computer or computing device. In simpler terms, it’s the “brains” behind your computer.
It is responsible for fetching data and instructions from memory, decoding and executing those instructions, and storing the results back in memory or sending them to output devices.
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The instructions a CPU can understand and execute are defined by its instruction set architecture (ISA). An instruction set is a set of basic commands that a processor can recognize and carry out. These instructions tell the CPU what operations to perform, such as adding or moving data, and how to perform them.
CISC vs RISC Architectures
CPU architectures can be broadly classified into two categories: CISC (Complex Instruction Set Computer) and RISC (Reduced Instruction Set Computer). The x86 and x64 architectures fall under the CISC category, while ARM is a RISC architecture.
CISC architectures have a larger and more complex instruction set, with each instruction capable of performing multiple operations. This can make CISC processors more efficient for certain tasks, as they require fewer instructions to accomplish the same goal. However, this complexity can also lead to larger chip sizes and higher power consumption.
On the other hand, RISC architectures have a smaller and simpler instruction set, with each instruction typically performing a single operation. This simplicity allows for more efficient execution and lower power consumption, making RISC processors well-suited for embedded systems and mobile devices.
X86: The Classic Architecture That Paved the Way
The x86 architecture, a CISC design, has been the dominant mainstream architecture for Windows PCs for decades. Launched in 1978 by Intel, it was the standard for over 20 years until the arrival of x64 in 2003.
Also known as the “32-bit” architecture, x86 operates within 32-bit RAM limitations, meaning no more than 4 gigabytes of system memory is visible to an x86 CPU.
Despite its age, the x86 architecture is renowned for its backward compatibility, allowing newer processors to run software designed for older versions.
This legacy support has been both a strength and a weakness, as it has ensured a smooth transition for users and developers but also carried historical baggage that can sometimes lead to inefficiencies.
X64: The 64-Bit Extension That Expanded Horizons
x64, also known as x86-64, is a CISC architecture and the current dominant architecture for Windows and Linux PCs. Built on top of the original x86 instruction set, x64 preserves software compatibility while offering 64-bit computing capabilities.
This evolutionary approach made sense as a measure to preserve the vast software ecosystem that had been developed for x86 over the years.
The most significant advantage of x64 over its 32-bit counterpart is its ability to handle larger amounts of memory and perform more complex calculations. With 64-bit addressing, x64 processors can theoretically access up to 16.8 million terabytes of RAM, although in practice, modern operating systems are limited to around 6 terabytes due to other factors.
This expanded memory capability has made x64 the architecture of choice for demanding applications such as video editing, 3D rendering, scientific simulations, and high-performance computing.
ARM: The Power-Efficient Alternative 
ARM (Advanced RISC Machine) is a RISC architecture, designed specifically for low-power, embedded systems like mobile devices and smartphones.
With its focus on simplicity and efficiency, ARM processors are highly power-efficient and generate less heat, making them ideal for battery-powered devices where energy consumption is a critical concern.
This is one of the reasons Apple’s M series of chips are so efficient compared to other chips from Intel and AMD.
Initially developed for the mobile and embedded market, ARM processors have undergone significant advancements in recent years, becoming increasingly powerful and capable of handling more complex workloads.
This has led to ARM challenging the dominance of x86 and x64 in the desktop and server markets, with companies like Apple adopting ARM-based processors for their Mac computers, a significant endorsement from the PC space.
Comparing the Architectures: Strengths and Weaknesses
Memory Capacity: In terms of memory capacity, x86 is severely limited, capped at 4 gigabytes of RAM, making it unsuitable for modern software demands and resource-intensive applications.
Both x64 and ARM, on the other hand, have significantly higher theoretical memory limits, with x64 supporting up to 6 terabytes of RAM in modern operating systems, while ARM is also capable of handling terabytes of memory, although specific limits vary across different ARM implementations.
Processing Power: While ARM functions on reduced complexity compared to x64, it has become remarkably capable for a wide range of software and applications, thanks to continuous advancements in ARM processor design. Apple’s M1 chips are a true testament to this.
However, x64 remains the dominant complex CPU architecture, leading the cutting-edge of high-end desktop (HEDT) and server motherboards, offering superior processing power for demanding workloads such as video editing, 3D rendering, scientific simulations, and high-performance computing tasks.
Power Consumption and Cooling Requirements: ARM excels in power efficiency due to its RISC design and lower power consumption. ARM devices generate significantly less heat than x64 or x86 systems, often negating the need for active cooling fans or extensive thermal management solutions.
This makes ARM processors ideal for mobile devices, where battery life and thermal management are critical factors.
Software Compatibility and Ecosystem: One of the strengths of the x86 and x64 architectures is their vast software ecosystem, with millions of applications and programs designed specifically for these architectures.
While ARM has made significant strides in software compatibility, particularly with the growing adoption of ARM-based desktop and server solutions, the x86/x64 ecosystem remains more mature and extensive.
In conclusion,
Each of these CPU architectures serves vital purposes in today’s hardware marketplace. x64 continues to dominate the high-performance computing segment, catering to professional editors, animators, gamers, and workstation users who require the utmost processing power and memory capacity.
Meanwhile, ARM has established itself as a power-efficient solution for mobile devices, embedded systems, and increasingly, low-power computing for web browsing, lightweight applications, and even desktop and server solutions.
While x86 has fallen by the wayside due to its obsolescence in the face of modern computing demands, its software legacy lives on within x64 and, to some extent, even certain ARM devices through emulation and compatibility layers.
The future of computing is likely to see a continued coexistence and evolution of these architectures, each playing to its strengths and addressing the diverse needs of the ever-changing technology landscape.
