Instruction Set Architecture Design: x86-64, ARMv9, and RISC-V, Fixed vs Variable Length, Register Files, Calling Conventions, and ISA Extensions

Deep End Era. Engineering with Sankalp · Oct 29, 2026 · 1h 5m

Why can a single x86-64 instruction be anywhere from one byte to fifteen bytes long, while every standard ARMv9 and RISC-V instruction is thirty-two bits—except when RISC-V squeezes half its instructions into sixteen bits? Why did AMD's 2003 sixteen-register extension save x86 from Intel's own Itanium, and why did UC Berkeley's RISC-V refuse to include carry and overflow condition flags? We open our ten-part computer architecture series at the fundamental contract between software and silicon.

Chapters

00:00:00 Opening: Three Hexadecimal Dumps and a Contract That Never Expires

00:04:38 What…