The APIs we have right now, they just allow us to queue synchronous workloads. We say, "draw some triangles," and then, "do some compute," and the driver can try to be a little smart, and maybe it'll overlap some of that. But for the most part, it's serial, and where we're doing one thing, it's not doing other things. With Mantle . . . we can schedule compute work in parallel with the normal graphics work. That allows for some really interesting optimizations that will really help your overall frame rate and how . . . with less power, you can achieve higher frame rates.
What we'd see, for example—say we're rendering shadow maps. There's really not much compute going on. . . . Compute units are basically sitting there being idle. If, at the same time, we are able to do post-processing effects—say maybe even the post-processing from a previous frame, or what we could do in Tomb Raider, [where] we have TressFX hair simulations, which can be quite expensive—we can do that in parallel, in compute, with these other graphics tasks, and effectively, they can become close to zero cost.
If we guessed that maybe only 50% of that compute power was utilized, the theoretical number—and we won't reach that, but in theory, we might be able to get up to 50% better GPU performance from overlapping compute work, if you would be able to find enough compute work to really fill it up.