Could someone explain why array writes are so expensive? I understand that a write would mark a cache line as dirty (significantly increasing eviction time caus

Could someone explain why array writes are so expensive? I understand that a write would mark a cache line as dirty (significantly increasing eviction time cause you have to write-back) and that it could probably prevent the compiler from enregistering stuff. However, I don't get the aliasing and the "a write is really a read and a write" argument.