Yep, but first you have to load this counter and increment it manually in some CPU register. And you also need to repeat the whole sequence in case CMPXCHG8B fa

Yep, but first you have to load this counter and increment it manually in some CPU register. And you also need to repeat the whole sequence in case CMPXCHG8B fails. With 32 bit integers you just execute XADD and move on with your life.