Apart from the cutting-edge APUs (like AMD Kaveri implementing hUMA), the memory of integrated GPUs and previous generation APUs was separate and copying chunks

Apart from the cutting-edge APUs (like AMD Kaveri implementing hUMA), the memory of integrated GPUs and previous generation APUs was separate and copying chunks of it in between happened via the bus. Plus since we're talking about cutting-edge gaming, integrated graphics is irrelevant (and so are APUs).