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Image Quality Comparison And Wrap-Up

AMD Mantle: A Graphics API Tested In Depth
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Image Quality Comparison: Mantle vs. DirectX

When the Mantle patch first launched, we saw evidence of inconsistent visual output using the newer API compared to DirectX 11 in Battlefield 4. So, I took some screenshots in the two games we tested for a comparison. Here are the results:

Previously, it was reported that there was a difference in saturation and contrast between Mantle and DirectX in Battlefield 4. But at this point in development, the disparity is apparently gone. We know DICE addressed the bug publicly and claimed to have fixed it in a subsequent patch.

As for Thief, I didn't find any meaningful image quality disparities between Mantle and DirectX.

How does Mantle impact the future of gaming?

Today we thoroughly tested the only two benchmarkable titles with AMD Mantle support. Thief exhibits clear (and impressive) performance gains under the API and really does mitigate much of the platform-oriented bottleneck imposed by low-cost CPUs. Battlefield 4 demonstrates gains with a Radeon R9 290X, while mid-range and low-end discrete cards suffer from what AMD suggests is a memory-related issue under Mantle. I tested a Radeon R9 270X with 4 GB as verification, and while Mantle didn't hurt performance, it also didn't enjoy an advantage. AMD says Mantle is in its beta stage, and so perhaps anomalies like this are expected as we sort through corner cases.

Regardless, based on most of our tests (and developer testimony), it's pretty clear that Mantle offers certain advantages over DirectX 11, at least. We don't have any OpenGL-based games to compare, but the claim is that both entrenched graphics APIs are limited compared to Mantle. So, what does that mean for you as a PC user?

In the short to medium term, Mantle may provide owners of GCN-based Radeon cards a performance boost in a very short list of games. That speed-up will be minimal on platforms with fast host processors like Intel's Core i7. But it should be more significant on lower-end CPUs like the FX-4170, A10 APU, or Athlon X4.

The list of Mantle-capable games will grow in the months to come. But even if you go by AMD's count, the total isn't large. Developers who find DirectX 11 too constraining for their engine may find it worthwhile to invest in a Mantle code path. Of course, that's extra work necessitating additional resources. In this way, Mantle is currently an equivalent to Nvidia's PhysX: a vendor-specific benefit in a small number of titles.

Step out further. Once AMD introduces its Mantle SDK, it's theoretically possible for Intel and Nvidia to develop a Mantle-compatible driver, which would probably give the ISV community more impetus to jump on the bandwagon. Frankly, this is unlikely. It doesn't make a lot of sense to hitch your cart to a horse driven by a competitor. Intel has reportedly asked for access to the Mantle SDK, but this is probably for internal testing purposes.

That brings us to the long game, which is where AMD's collective head has to be right now. Will there be a place for Mantle once DirectX 12 arrives, with its own take on minimalism and the ability to execute fully parallel draw submissions concurrently on multiple CPU cores? It seems pretty clear that Intel and Nvidia will embrace the Microsoft option. I suppose that if Mantle is closely compatible with DirectX 12, developers might be willing to invest some development time to support it. But AMD will inevitably support DirectX 12 too, so the work could be redundant. Once DirectX begins propagating, Mantle's biggest strength will be its ability to expose any new Radeon-exclusive features quickly for developers who want to access them, a la 3dfx's Glide.

Of course, the discussion emphasizes PCs, but consoles are in play here as well. If Microsoft and Sony were to embrace Mantle on their AMD-based platforms with lightweight Jaguar-based x86 cores, the API would almost necessarily enjoy a leap in developer support. Much of the PC game library is ported from (or at least developed concurrently with) console builds. Microsoft naturally has the incentive to wait until DirectX 12 is ready. As for Sony, the PlayStation 4 has its own API, which is advanced compared to DirectX 11 and OpenGL. Johan Andersson, DICE's lead graphics programmer, has said that the “PS4 graphics API is good as well; we don’t need Mantle on PS4.”

Really, the unknown quantity could be Valve's Steambox. While AMD currently doesn't support Mantle in its Linux driver, the company hinted it might be possible in the future. Assuming Valve can figure out how to make its concept hold some value (right now, we have a hard time seeing it), there may be demand for Mantle there. SteamOS has a long way to go before this is a significant factor, though.

In the meantime, Mantle does represent innovation. Even if it's eclipsed by DirectX 12, there's every reason to believe that Mantle is what spurred Microsoft into motion on its next-gen graphics API. Clearly, there was a real need or desire to eradicate overhead affecting the gaming experience. And whether AMD compelled action or the development was concurrent, AMD got its message out first. For now, and until AMD makes more notable overtures to the industry, we're looking at it as a value-added feature like PhysX. We don't mean this in a technical sense, obviously, but in the sense that it provides an advantage to one graphics card manufacturer in a handful of games.

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