Fences neither guarantee, nor are required, to hit RAM. You are thinking of flush (for writes) and invalidate (for reads). Alternatively, just ping N+1 addres

Fences neither guarantee, nor are required, to hit RAM. You are thinking of flush (for writes) and invalidate (for reads). Alternatively, just ping N+1 addresses that share a cache slot (where N is the way-ness of your cache). (Fences guarantee only memory ordering, and are typically implemented by flushing to cache, not to RAM.)