In our test conditions, Mantle's impact on Battlefield 4 performance is relatively underwhelming – for the vast majority of our tests improvements stayed well under 10 percent and even then they rarely resulted in a gaming experience that was visibly improved from our standpoint. For most users or mid-range and high-end systems (or even low-end ones reliant on integrated GPUs), CPU limitations probably won't be a concern before GPU-limitations in Battlefield 4, so the advantages to be felt will be slim.
As we initially said, however, it's still very early days for Mantle. There could still be more to come and it's important to remember that our benchmarks are limited to the single player portion of the game out of a necessity to keep them repeatable and reliable – in 64-player multiplayer maps, for example, things are likely to be much more hectic than they are here, and the CPU will be relied upon more heavily.
This itself is important to remember as our tests showed that there is a tipping point where, with the right set-up, the CPU can be a clear limiting factor on the GPU's performance, which is why we saw a 37 percent framerate increase between DirectX and Mantle using an R9 290X at 1080p medium with an underclocked CPU. In this example, in real world terms, the difference doesn't mean much, as even when the Direct3D API is limiting things the card is more than capable of averaging over 120fps. However, it's at least plausible that certain set-ups (perhaps users who have focussed on GPU upgrades over the years) will obtain improvements that are actually beneficial in terms of the actual gaming experience and not just framerates, we just don't think it will be that common.
Whatever your views on Mantle, the fact is that AMD is committed to it and it's here to stay. In the coming months stability and performance is likely to improve, and users of the right hardware can expect a small (but free) performance boost in Battlefield 4. Even now, however (and especially in the future), Mantle does extend beyond the world of Battlefield 4. While you should always take benchmark results that come straight from manufacturers with a pinch of salt, the chart above does imply that Mantle can have a huge impact even when you're already using a very powerful CPU – the draw call bottleneck is very real. Only time will tell specifically how Mantle will go on to be used in future projects and the impact it will have on the wider PC gaming environment, but it's an interesting addition to the ride nonetheless.