CPU reordering

It is good to consider that the CPU is actually reordering the instructions, as opposed to an abstract list of memory operations. Thinking in terms of instruction reordering lets us assume that once the instruction is finally executed, all cores will immediately see that new value in memory. It also lets us understand the CPU from the point of the user program rather than trying to understand the internals. For normal user programming this view is correct.

Source: http://eversystems.eu/Document/26/CPU_Reordering_-_What_is_actually_being_reordered