What Is RISC-V? The Open Instruction Set, Explained

RISC-V (pronounced “risk-five”) is an open, royalty-free instruction set architecture — the vocabulary of binary instructions a processor understands. Anyone can implement it in a chip without paying licensing fees or asking permission. That single property is what makes it different: for decades, a chip’s instruction set was owned by someone — x86 by Intel and AMD under strict licensing terms, Arm by a company that charges royalties for every chip design that uses it. RISC-V arrived as a direct challenge to that model.

What an ISA is and why “open” matters

An instruction set architecture (ISA) is the contract between hardware and software. Compilers, operating systems, and firmware target an ISA; processors implement it. Once software exists for an ISA, there is enormous pressure to stay compatible — which is why x86 compatibility has persisted for decades despite the architecture’s complexity.

“Open and royalty-free” changes the economics of chip design in several ways:

• No licensing fees. A startup, a university, or a government research lab can design a RISC-V chip without writing checks to a licensor. Arm’s model charges an upfront license plus a royalty on every chip sold; at the volumes of embedded silicon, that difference compounds into real money.
• No vendor lock-in. A company building an embedded system on RISC-V is not dependent on Arm’s licensing terms or Intel’s roadmap. If a better RISC-V core appears, you can switch without a licensing renegotiation.
• Auditable. Open specifications allow independent security audits, which matters in regulated industries and government procurement. This has become a significant geopolitical driver, discussed below.

Where RISC-V came from

RISC-V began in 2010 at UC Berkeley as a teaching and research project — the fifth in Berkeley’s line of RISC (reduced instruction set computer) designs, hence the “V.” The designers wanted an ISA free of the legal encumbrances that made x86 and Arm off-limits for open research, and published it under open licenses. A foundation formed in 2015 to steward the specification; it later reorganized as RISC-V International and moved to Switzerland in 2020, placing the standard’s governance deliberately outside any single country’s jurisdiction.

The modular design

RISC-V is designed as a small, stable base plus optional extensions. This modularity is a deliberate feature: a microcontroller in a sensor node does not need floating-point hardware, and a high-performance CPU does not need to be defined by the same spec.

Component	Description
RV32I / RV64I	Base integer instruction set (32-bit or 64-bit). Mandatory and frozen — software targeting this will always run.
M extension	Integer multiply and divide
A extension	Atomic operations (load-reserved / store-conditional)
F extension	Single-precision floating-point
D extension	Double-precision floating-point
C extension	Compressed 16-bit instructions (reduces code size)
V extension	Vector processing

A chip’s capability is often described with a shorthand: RV64GC means a 64-bit base plus the G grouping (M+A+F+D, the standard general-purpose set) plus compressed instructions. This is the profile most Linux-capable RISC-V SoCs target.

The vector extension (V) is particularly relevant for AI and ML workloads, enabling wide SIMD operations on custom silicon without reaching for proprietary extensions.

RISC-V vs x86 vs Arm

	x86	Arm	RISC-V
Licensing	Closed — Intel and AMD only	Per-design license + per-chip royalty	Free and open
Who can implement it	Effectively no new entrants	Paying licensees	Anyone
Custom instructions	No	Restricted	Explicitly supported via extensions
Software ecosystem	Deepest (PCs, servers)	Deep (mobile-first, growing servers)	Growing fast, gaps at the top
Strongholds	Desktops, laptops, servers	Phones, embedded, expanding into PCs and cloud	Microcontrollers, controllers, accelerators

The comparison also explains the strategy. Arm spent two decades proving a licensed ISA could dethrone x86 outside the PC — and is still pushing into Windows laptops and the data center. RISC-V is running the same playbook one step further: not just a cheaper license, but no license at all.

Where RISC-V is winning

Microcontrollers and embedded. This is where RISC-V already has serious commercial traction. Dozens of vendors ship RISC-V cores for IoT sensors, motor controllers, and industrial devices. The small base ISA is a good fit for constrained hardware, and the licensing model is a hard advantage over Arm Cortex-M at scale.

Storage controllers and networking. Internal controllers — the processors running SSD firmware, RAID cards, and network interface cards — are exactly the kind of specialized compute that benefits from a custom ISA implementation tuned to the workload. Several major storage vendors have moved internal controllers to RISC-V. Chances are good you already own RISC-V silicon without knowing it.

AI/ML accelerators. This is an area of rapid growth. Custom AI chips almost always pair domain-specific execution units for matrix multiplication — the same kind of workload a GPU or NPU accelerates — with a general-purpose control core. Choosing RISC-V for that control core rather than a licensed Arm core saves royalties and allows deeper customization of the instruction set via extensions. Several AI accelerator startups have chosen RISC-V for precisely this reason. The intersection with software-defined hardware is also a natural fit with the kind of portable compilation targets that WebAssembly is developing.

Where it is still maturing

High-end application processors. Running a competitive mobile SoC or desktop-class CPU requires years of microarchitectural investment. The leading x86 and Arm application processors reflect decades of incremental optimization in branch prediction, out-of-order execution, cache hierarchies, and power management. RISC-V cores are catching up but are not yet competitive at the high end for general-purpose compute — the segment where custom data-center silicon bets are still being made on Arm.

Software ecosystem. Linux, GCC, LLVM, and most major open-source runtimes support RISC-V. But the commercial software layer — proprietary databases, security software, specialized enterprise tools — has limited RISC-V support. For server-class deployments, the ecosystem gap with x86 remains significant. The toolchain and systems programming landscape, including languages like Rust that have invested in RISC-V targets, is helping close this gap from the developer side.

Fragmentation risk. Modularity cuts both ways: if every vendor ships a different mix of extensions, binaries stop being portable. The ecosystem’s answer is profiles — standardized bundles of extensions (such as the RVA series for application processors) that operating systems and distributions can target as a single platform. Profile adoption is one of the clearest signals of the architecture growing up.

The geopolitical dimension

RISC-V’s momentum is not purely technical. Several factors have made the open ISA politically attractive:

Chip supply chain security. Governments and large organizations that want to audit or fully control their compute stack find it easier with an open, unencumbered architecture. China in particular has invested heavily in RISC-V development as a path to domestic chip independence from Western-controlled architectures.

Sanctions and export control resilience. Arm and x86 are both controlled by companies subject to US export regulations. An open architecture maintained by a Swiss foundation (RISC-V International) is structurally harder to subject to the same controls.

Academic and research use. Universities worldwide now teach computer architecture using RISC-V, and the next generation of hardware engineers is learning on an open ISA. That pipeline effect compounds: engineers design with what they know.

What to watch

The near-term signals to track: whether any RISC-V application processor reaches competitive performance with mid-range Arm cores; whether the vector and hypervisor extensions — and the profiles that bundle them — become widely implemented; and whether major cloud providers begin offering RISC-V instances (a signal of ecosystem maturity). The progress from “interesting embedded option” to “credible server architecture” would mark a genuine structural shift in the chip industry.

The takeaway

RISC-V is an open, royalty-free instruction set — a standard anyone can build a processor around, governed by a neutral foundation rather than a vendor. It will not displace x86 or Arm in high-performance general computing any time soon. What it has already done is demonstrate that an open ISA can achieve real commercial adoption, that the licensing-free model attracts serious investment, and that the geopolitical and economic pressures driving that investment are not going away. For embedded, accelerators, and custom silicon, RISC-V is already a first-class choice. The rest is a matter of time and ecosystem maturation.