How many registers does an x86-64 CPU have? (2020)

Re:How many registers does an x86-64 CPU have? (2020) by mjevans on Saturday February 14, 2026 @11:57AM (#47016072)

I recalled there were some new instructions added that greatly help with this. Unfortunately I'm not finding any good _webpages_ that describe the operation generally to give me a good overview / refresher. Everything seems to either directly quote published PDF documents or otherwise not actually present the information in it's effective for end use form. E.G. https://www.felixcloutier.com/x86/ -- However availability is problematic for even slightly older silicon https://en.wikipedia.org/wiki/X86-64

- XSAVE / XRSTOR

- XSAVEOPT / XRSTOR

- XSAVEC / XRSTOR

- XSAVES / XRSTORS

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Re:How many registers does an x86-64 CPU have? (2020) by Joker_vD on Saturday February 14, 2026 @09:50PM (#47020597)

Eh, pretty much nobody uses them (outside of OS kernels?); and mind you, RISC-V with its 32 registers has nothing similar to those, which is why 14-instruction long prologues (adjust sp, save lr and s0 through s12) and epilogues are not that uncommon there.

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