Difference Between RISC-V And ARM Processors

We live in a digitally connected world, where our professional and personal lives often revolve around smartphones, computers, tablets, wearable technology, and others. Luckily, we aren’t as connected as most of the people in The Matrix were, and don’t have to fight machines to regain control of the planet.

Most of these devices help us enjoy entertainment options, track our health, and communicate with others remotely. Yet, how do these devices communicate within themselves?

Of course, we know they’re all powered by microchips or microprocessors, but what form of communication do microprocessors engage in? How do they receive instructions on what applications to run or how to run them?

This is where processor architecture and instruction set architecture (ISA) comes in—with RISC-V and ARM being two of the most influential ISAs.


So, before we dive deep into the differences between our two contestants, let’s just recap the basics.
 

What Are Processor Architectures?

Processor architecture describes the design and organization of a CPU (central processing unit), a computer’s “brain,” including determining the data paths, memory addresses and other aspects. Essentially, it determines how a processor executes instructions, manages data, and interacts with other system components.

While there are a series of different types, the two most commonly used process architectures include Reduced Instruction Set Computing (RISC) and Complex Instruction Set Computing (CISC).

Don’t worry if it’s the first time you’re reading these terms–we have a complete lowdown on them!
 

What Is Reduced Instruction Set Computing (RISC)?

RISC focuses on simple, fast instructions that enable faster execution and less power consumption. Typically, RISC is known for its high performance and energy efficiency.

Both RISC-V and ARM processor architectures fall under this category, and extend to include architectures such as PowerPC architecture (developed by an alliance of Apple, IBM, and Motorola—AIM), MIPS (Microprocessor without Interlocked Pipeline Stages), ColdFire (a microcontroller (MCU) architecture), TriCore (a multi-core, multi-threaded processor architecture), and others.

Easy, right?
 

What Is Complex Instruction Set Computing (CISC)?

CISC uses a larger, more complex instruction set with high code density. This architecture can perform a variety of tasks offering efficient use of memory and is highly effective in areas that require a high degree of parallel processing, such as gaming and video editing.

Being commonly used in personal computers and laptops, the most prominent processor architecture in this category is Intel’s x86 (derived from the Intel 8086 microprocessor), which also inspired processors built by AMD.

Now, to the million-dollar question...
 

What Are Instruction Set Architectures (ISAs)?

Instruction Set Architecture (ISA) acts as an interface between a device’s hardware and software. Essentially, ISAs set the instructions for execution, specifying what a processor can do and how it needs to be done. They are the blueprints that define how a processor executes instructions, and outline their performance, capabilities, compatibility, and power efficiency.

There are two kinds of ISAs: Closed (proprietary) and open (free to use). While there are numerous instruction set architectures, RISC-V and ARM are two of the most popular ones in use today.

So, let’s learn more about them!
 

What Is RISC-V?

First things first, it’s pronounced “risk-five.”

RISC-V is an open-source instruction set architecture (ISA) that offers efficient and versatile usage in computing devices. Open source means it’s free to use, modify, and deploy as users see fit, without having to worry about licensing fees. Other than being free to use, it’s gained prominence for being simple, flexible and scalable, while its modular structure enables customization.

This architecture is used by manufacturers, researchers, and innovators to build processors with diverse performance levels, enabling data centers, supercomputers, consumer electronics, and more.

Need more information about what RISC-V is and how it works?
 

What Is ARM?

ARM is an acronym for Advanced RISC Machine.

ARM is an instruction set architecture (ISA) owned by Arm Holdings (formerly known as Advanced RISC Machines), a subsidiary of SoftBank Group. This means that it’s a proprietary ISA that’s licensable—an extremely popular one at that—enabling manufacturers to customize designs for specific applications.

ARM follows the Reduced Instruction Set Computing (RISC) approach, offering energy-efficient, high-performance, fast processing. It’s used in devices such as smartphones, tablets, IoT devices, automotive electronics, industrial machinery, and more.

Still wondering what an ARM processor is?
 

What Are The Differences Between RISC-V And ARM Processors?

While they may fall under the same category of processor architecture types and bear numerous similarities, their differences can be as contrasting as Morpheus’ red and blue pills do.

Picking between RISC-V and ARM processors can present an actual “Sophie’s Choice” moment for manufacturers. So, what are the main differences between the two?

 

• Licensing

  RISC-V is open source and therefore, is free for anyone to use in any way. This means that companies aren’t restricted by licensing requirements, allowing them to freely innovate. It also means that they enjoy freedom from vendor lock-in constraints, allowing them to choose whichever software and hardware they wish.
  
  ARM in-turn, comes as proprietary architecture, meaning that manufacturers must secure licensing agreements by its developer—ARM Holdings. As such, ARM offers multiple licensing tiers that allows companies to choose diverse instruction sets and architectures based on their respective requirements.

• Cost

  Open source translates to free use, meaning RISC-V offers companies more cost-effectiveness. This trait also simplifies development, verification, and manufacturing procedures by reducing expenses related to instruction set design.
  
  ARM’s proprietary nature means that it infuses licensing complexities and costs, reducing cost-effectiveness. ARM also includes royalties based on the chips that its customers sell and typically range from 1 to 2% of the chip's selling price.

• Customization

  Being open-source enables RISC-V to offer more flexibility and customization, allowing companies to tailor their ISA to their unique needs while also boosting performance and power efficiency. This enables startups and researchers the room for experimentation and rapid prototyping.
  
  ARM’s proprietary nature requires companies to source licensing rights limiting growth speed, but it does come with some level of configurability through extensions. Additionally, ARM offers comprehensive development kits—which include indispensable tools, documentation, and support—that enable companies to streamline and quicken their prototyping process.

• Instruction Set

  RISC-V uses a load-store architecture, a fixed-length 32-bit instruction encoding format, and a small set of general-purpose registers that simplify decoding logic. It supports a range of integer instruction set extensions, including RV32I (32-bit), RV64I (64-bit), and RV128I (128-bit), and uses little-endian byte ordering.
  
  ARM also uses a load-store architecture but comes with a blend of fixed-length 32-bit and variable-length Thumb instructions, and a large set of general-purpose registers. This can improve code density but also increase complexity to decoding logic. It utilizes bi-endian byte ordering, allowing processors to handle both little-endian and big-endian data formats at the hardware level, and spans multiple processor families.

• Support

  Typically, open-source projects don’t offer brilliant customer support, unless the project possesses a massive fan base—fortunately, RISC-V does! It consists of a large ecosystem of companies, startups, developers, and researchers, which enables collaboration and contribution to a shared pool of knowledge and innovation. As it continues to grow in popularity, the growing ecosystem shows promise of a stable, sustainable future with continued availability and support.
  
  ARM is owned by ARM Holdings, which comes with the backing of SoftBank Group, meaning that companies using this architecture enjoy full and exceptional support and liability coverage of ARM Holdings. Furthermore, ARM’s well-established ecosystem also offers the knowledge and wisdom from various vendors, spanning a wide range of processors, development tools, and support.

• Security

  RISC-V enables companies, researchers, and developers to directly control security measures. The transparency and accessibility that comes with its open-source characteristics, allow them to scrutinize its architecture and identify vulnerabilities, which they can then customize to meet their unique requirements.
  
  ARM’s architecture means its security is based on the measures provided by ARM Holdings and its partners. In critical sectors such as military operations, financial processes, data-sensitive sectors, and others, hardware security is of paramount importance—not having customized control over security could be a concern.

• Market Share

  While over 10 billion RISC-V cores are in use across various applications globally, ARM architecture controls a massive 95% of the smartphone market. On the whole, ARM remains the prevailing architecture when compared to RISC-V. A large part of this is due to its mature ecosystem, decades-long presence, exceptional support, and diverse performance cores. Despite its open-source nature, RISC-V trails ARM in market penetration.

• Real-Time Applications

  When it comes to real-time applications, RISC-V and ARM come with diverse advantages. ARM brings in well-tested solutions courtesy of its mature ecosystem, and RISC-V offers customizations that allow developers to remove features that may introduce unpredictability, optimizing devices for real-time applications.

Conclusion

Just like Neo’s choice between the red and blue pill, selecting between RISC-V and ARM isn’t about which is “better” universally—it’s about which unlocks the right kind of reality for your specific use case. Do you want the open-source freedom, customization, and collaborative power of RISC-V? Or the tried-and-tested, well-supported, and globally dominant infrastructure of ARM?

Each path takes you down a different rabbit hole—one paved with experimentation, the other with reliability. The question is, which one will you choose, Neo?