Here is a good little read from BF4 Battlelog:
Give a few example of different systems on different levels:http://battlelog.battlefield.com/bf4/news/view/bf4-mantle-live/
"Battlefield 4 on PC is already quite heavily optimized using DirectX 11 and DirectX 11.1, but with Mantle we are able to go even further: we’ve significantly reduced CPU cost in our rendering, efficiently parallelized it over multiple CPU cores and reduced overhead in many areas.
The biggest performance gains can be seen when the game is bottlenecked by the CPU which can be quite common even on high-end machines and this was main goal to improve on with Mantle. We’ve also been able to streamline and optimize some of the GPU workload. The end result is that game performance is improved in virtually all scenarios in Battlefield 4 on both Windows 7 and Windows 8 when running with Mantle!"Edited by weetbix07 - 1/31/14 at 4:56am