Traditionally I like to look at the benchmarks from Anandtech’s review. And their findings fit exactly with the prediction I made earlier: a high-end setup will likely see 10-15% gain at best. The lower the graphics detail, the more Mantle is able to gain… But why would anyone run on less than Ultra settings with an R9 290X?
Although Direct3D is slightly slower, it still gets well over 60 fps on average, so those few extra FPS that Mantle gives you, aren’t all that relevant. Note also that even underclocking the CPU to 2 GHz and disabling some cores does not affect performance. So you certainly don’t need a fullblown i7-4960X to get these framerates in Direct3D mode. It also seems that Mantle does not do all that much for multithreading, although this was one of the claims made by AMD/DICE initially.
So the first impression is that Mantle is just not that interesting. Its gains are mainly in unrealistic scenarios: running very low detail settings on a high-end rig, or combining a low-end CPU with a top-of-the-line GPU.
I don’t think these gains are much incentive for most developers to start supporting Mantle in their games. Also, these gains will only get smaller over time. CPUs keep getting faster, so the low-end will continue to move up as well. And Direct3D and OpenGL will also continue to reduce CPU overhead in future versions. Which also means that there is little incentive for Intel and nVidia to want to support Mantle themselves.
After all the hype, these results are a bit of a letdown. Mantle does not look like it’s going to be the revolution it was hyped to be. It looks like a short-term solution to a problem that is disappearing anyway.
Update: At Tech Report, they actually bothered to test an nVidia card as well. It turned out to be a lot less CPU-limited in Direct3D than the AMD cards:
One thing we didn’t expect to see was Nvidia’s Direct3D driver performing so much better than AMD’s. We don’t often test different GPU brands in CPU-constrained scenarios, but perhaps we should. Looks like Nvidia has done quite a bit of work polishing its D3D driver for low CPU overhead.