Here is a great article on the topic. Basically, x86 spends a comparatively enormous amount of energy ensuring that its strong memory guarantees are not violated, even in cases where such violations would not affect program behavior. As it turns out, the majority of modern multithreaded programs only occasionally rely on these guarantees, and including special (expensive) instructions to provide these guarantees when necessary is still beneficial for performance/efficiency in the long run.
Here is a great article on the topic. Basically, x86 spends a comparatively enormous amount of energy ensuring that its strong memory guarantees are not violated, even in cases where such violations would not affect program behavior. As it turns out, the majority of modern multithreaded programs only occasionally rely on these guarantees, and including special (expensive) instructions to provide these guarantees when necessary is still beneficial for performance/efficiency in the long run.
For additional context, the special sauce behind Apple’s Rosetta 2 is that the M family of SoCs actually implement an x86 memory model mode that is selectively enabled when executing dynamically translated multithreaded x86 programs.