ARM vs RISC-V vs x86: Instruction Set Architectures Compared

ARM, RISC-V and x86 are three instruction set architectures (ISAs): the contract between software and a processor. ARM and RISC-V are RISC designs, while x86 is a CISC design that has grown over decades. The biggest differences are in who may build them and how big the software ecosystem is. x86 dominates PCs and servers, ARM dominates phones and is growing in laptops and servers, and RISC-V is an open standard that is spreading fast in embedded systems.

AspectARMRISC-Vx86
Design styleRISC, load/store architectureRISC, load/store architecture, modularCISC, with many complex instructions and memory operands
Instruction lengthFixed 32 bits in the 64-bit mode (AArch64)32 bits, plus optional 16-bit compressed instructionsVariable, 1 to 15 bytes
General-purpose registers31 (AArch64)32 (x0 always reads as zero)16 (x86-64)
LicensingProprietary: companies license it from Arm Ltd and pay fees and royaltiesOpen standard: anyone can build a chip without license feesProprietary: in practice only Intel and AMD build x86 processors
ModularityProfiles for applications (A), real-time (R) and microcontrollers (M)A small base plus optional extensions (such as multiply, floating point, vector)Extensions added over decades (SSE, AVX and more), keeping old software working
Software ecosystemMature: mobile, Linux, macOS on Apple silicon, Windows on ArmGrowing quickly, strongest in embedded systems and LinuxThe largest, especially for Windows and legacy desktop and server software
Main strengthsPower efficiency and a wide range from microcontrollers to serversCustomization and no license costHigh single-thread performance and software compatibility
Typical usesSmartphones, tablets, Apple Macs, cloud servers, embeddedEmbedded and IoT, accelerators, education, emerging serversPCs, servers, workstations

Figures are typical orders of magnitude and vary by process generation and product.

When to use which

ARM
When power efficiency matters and you want a proven ecosystem, from phones to cloud servers.
RISC-V
When you want to design your own processor, avoid license fees, or add custom instructions.
x86
When compatibility with existing PC and server software is the priority.

FAQ

Is ARM faster than x86?

Not inherently. Performance depends on the specific processor design and manufacturing process. ARM designs tend to be more power-efficient, while x86 designs have often led in peak single-thread performance.

Why is RISC-V free?

RISC-V is an open standard managed by RISC-V International, so anyone can build a chip with it without paying license fees. ARM and x86 are proprietary.

Can ARM software run on x86, and the reverse?

Not directly, because the instruction sets differ. Programs must be recompiled, or run through an emulator or a translation layer.

Which processors do Apple Macs use?

Apple silicon Macs use ARM-based processors designed by Apple.

Check your understanding

What do names like ARM, x86 and RISC-V mainly refer to?

  1. AGenerations of manufacturing processes
  2. BInstruction set architectures (ISAs)
  3. CTypes of packages
Show answer and explanation

Answer: B. Instruction set architectures (ISAs)

ARM, x86 and RISC-V are instruction set architectures (ISAs)—the contract between software and hardware defining instructions, registers and memory behavior. Processors implementing the same ISA run the same programs even if designed by different companies. x86 (Intel, AMD) dominates PCs and servers, ARM powers smartphones and Apple Macs, and RISC-V is spreading, mainly in embedded systems.

Which is a characteristic of RISC-V?

  1. AIt is a proprietary instruction set that only one company can use
  2. BIt is an instruction set exclusively for GPUs
  3. CIt is an instruction set architecture with an open specification that can be used without license fees
Show answer and explanation

Answer: C. It is an instruction set architecture with an open specification that can be used without license fees

RISC-V is an open ISA begun at UC Berkeley in 2010; its specification is public and anyone may implement it without license fees. The base integer set has only about 40 instructions, with optional extensions—floating point, vector and more—chosen per application. Custom instructions can be added too, so it is spreading in embedded microcontrollers, storage controllers and AI accelerators.

Which is a characteristic of RISC (reduced instruction set computer)?

  1. AIt has many complex instructions of varying length
  2. BIt limits instructions to a small number of simple ones, making pipelining easier
  3. CIt has no instructions at all
Show answer and explanation

Answer: B. It limits instructions to a small number of simple ones, making pipelining easier

RISC limits instructions to simple, uniform-length operations, performs arithmetic only between registers and restricts memory access to load/store instructions. Uniform execution times suit pipelining; ARM and RISC-V are leading examples. CISC designs such as x86 now decode their complex instructions into simple internal micro-ops, so the practical gap has narrowed.

  1. Which statement is correct about two CPUs that implement the same instruction set architecture (ISA)?
  2. What is a characteristic of a load-store architecture such as RISC-V?

Practice CPUs and architecture questions

Key terms explained

Instruction set architecture (ISA)
The processor specification as seen by software, including the instructions and registers it supports. Examples include x86, Arm and RISC-V.

Related comparisons