When we first tested Thief we were shocked by how poorly AMD's processors performed so we were expecting Mantle to have a big impact when using the company's CPUs in this game. That was the case.
With the R9 290X installed, Mantle didn't do much for the Intel processors with the Core i7-4770 and Core i3-4130 setups hitting 42fps using both Mantle and DX11. There were gains to be had at 1920x1200 and 1680x1050, but these lower resolutions aren't really desirable with this graphics card.
The FX-8350's performance on the other hand went from 33fps when using DX11 to a Core i7-like 42fps with Mantle. Although the A8-7600 didn't do quite as well, Mantle still pushed from a dismal 24fps to 40fps.
When using the R9 290X, Mantle again only offers around 5% more performance to Intel users. The best gain here was for the Core i3-4130 which was 9% faster at 1920x1200, but let's be honest, with this GPU most gamers will want to play at multi-monitor resolutions.
Mantle was a godsend for the FX-8350 and A8-7600. The A8-7600 enjoyed almost a 50% performance boost at 1920x1200 and almost 70% at 2560x1600. The FX-8350 also benefited handsomely from Mantle with almost 60% more performance at 1920x1200 and almost 30% more at 2560x1600.
The R9 280X managed 46fps at 1920x1200 when armed with the Core i7-4770 and 44fps with the Core i3-4130, while the FX-8350 was only good for 32fps and the A8-7600 just 28fps. Turning on Mantle boosted the Core i7-4770's performance by 1fps at 1920x1200 while the Core i3-4130 was 3fps faster, yet the FX-8350 enjoyed 12fps more and the A8-7600 allowed for 13fps more.
As you can see with the R9 280X, the Core i3-4130 was just 7% faster at 1920x1200 while the Core i7-4770 was only 2% faster when using AMD's API. However, the FX-8350 was 38% faster and the A8-7600 enjoyed 46% more performance.
When testing the R7 260X in Battlefield using Mantle it made this GPU slower across the board. This isn't quite the case when testing with Thief but the gains aren't exactly spectacular either.
At 1680x1050 the R7 260X was good for just 37fps which was achieved by the Core i7-4770 using both DX11 and Mantle. The Core i3-4130 managed 37fps with Mantle and 36fps with DX11.
The FX-8350 went from 33fps when using DX11 to a slightly faster 35fps with Mantle and the A8-7600 went from 28fps to a more playable 33fps with AMD's API.
Here we see no performance gains for the Core i7-4770 when paired with the Radeon R7 260X using Mantle. The Core i3-4130 was around 3% faster -- hardly worth mentioning since we're talking 1fps.
The FX-8350 gained nothing at 2560x1600 or 1920x1200 and was 6% faster at 1680x1050, while the A8-7600 gained nothing at 2560x1600, was 4% faster at 1920x1200 and enjoyed an 18% performance boost at 1680x1050.