How many registers does an x86-64 CPU have? (2020)
Summary
A thorough, methodology-driven look at how x86-64 registers are counted, including GPR subregisters, special and MSR registers, and vendor-specific caveats. The piece explains the rationale behind what gets counted, documents key totals (around 557 total registers and 400 architectural MSRs), and points to external resources for deeper exploration. It’s useful for developers needing low-level hardware context, OS/VM designers, and security researchers.