RISC-V and instruction sets compared

In short: An instruction set (ISA) defines which basic commands a processor understands. The three important ones are x86 (PCs and servers), ARM (phones, Apple, many servers) and the free RISC-V.

What an instruction set is

Programs are translated for an instruction set (compiler). A program for x86 does not run on ARM without being recompiled or emulated. The chip design behind it (pipeline, cache, see CPU structure) can be very different.

Two schools of thought

• CISC (x86): many, partly powerful commands of different length. The chip translates them internally into simpler steps.
• RISC (ARM, RISC-V): few, simple commands of equal length. Easier to build and often more economical.

The three compared

	x86-64	ARM (AArch64)	RISC-V
Spread	PCs, servers	phones, Apple Silicon, cloud	microcontrollers, research, growing
Licence	Intel and AMD	licence from Arm	open, free
Strength	software, performance	efficiency	freely adaptable

More on the first two: x86-64 and ARM64.

Why RISC-V matters

The instruction set is open: anyone may build chips for it without licence fees and permission. It is modular: a core with base commands (I) plus extensions (for example M multiplication, F/D floating point, V vectors). That suits small chips in devices as well as servers. Linux already runs on it (The Linux kernel in overview).

What developers notice

Most notice little: languages such as Python or Java run on all. Whoever distributes programs builds them for several architectures (e.g. container images for amd64 and arm64).

See also: CPU