> I can't point you to the exact working in the intel docs as they are quite messy, but you can implement a perfectly C++11 compliant SPSC queue purely with load and stores on x86 without any fences or #LOCK operations.

I would disagree. I think the Intel docs do not specify a guarantee of flushing, and so if the SP and SC are on different cores, I think then in principle (but not in practise) the SC could in fact never see what the SP emits.