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Computer Internals

Glossary

Instruction set architecture (ISA)

The contract between software and hardware: the instructions, registers, data types and encodings a processor promises to support.

x86-64, ARM64 and RISC-V are ISAs. Two very different chips can implement the same ISA — that's why the same binary runs on an Intel and an AMD processor — while the microarchitecture underneath is free to change.