4 ms·

And then you get an optimizing compiler and the slow behavior is back.

• mikeash 11y ago
  Or you get an optimizing compiler that's aware of this difference and automatically emits a read before a blind write.
  • TheLoneWolfling 11y ago
    ...Which makes things worse for any CPU that doesn't have this bug.
    • mikeash 11y ago
      It doesn't sound like a bug, just a legitimate difference in how things are done. In any case, CPU-specific optimizations are hardly rare.