alt Hacker NewsFrom my reading of the article I think they understood why we'd want these two primitives for CAS, but they weren't clear (whereas your answer is better here) on whether that's a thing we care about today in 2025. ARM vs x86-64 matters for many people today whereas if we only wanted the other primitive for the M68k well, sorry Amiga fans but who cares.
Without immersion in the "Why" of each technological niche it can be hard to judge whether you're reading advice that really hasn't been relevant in decades ("The ASCII character set is not supported on all computers") or that's still important to your work today ("The file naming conventions may vary from one system to another")
> whether that's a thing we care about today in 2025
Good question actually! ARM64 has a proper CAS it seems, but I think smaller ARMs still have only LL/SC and that's still relevant for embedded. I can't find a definitive answer for POWER, it is possible that is till only has LL/SC (I leave it to you whether POWER is still relevant, but certainly IBM cares that the standard support it, and it was still relevant during C++11 standardization). Can't find a definite answer for RISC-V: it seems that originally it only had LL/SC, but there are AMO extensions that add RISC-V.
I think most GPUs have native CAS instructions.
There are probably other embedded processors that are still relevant for C++, who knows what they support.