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by mdasen
862 days ago
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It seems unlikely that Power completely lacked atomics. This is a very vague recollection since it's been a long time, but I feel like there were some differences. I think PowerPC used a load-linked/store-conditional with a stronger guarantee than a CAS (compare and swap) on x86. For example, if x = 1 and you CAS it to a new value, another thread might have changed it to 8 and then back to 1 in the meantime and it'll still succeed (the ABA problem: https://en.wikipedia.org/wiki/ABA_problem). I think x86 also has a stronger memory model providing less flexibility, but greater consistency. |
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