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AMD Mantle Demo – Game still GPU-bound with CPU cut in half to 2GHz

Tyler Roemhildt
Dec 20, 2013
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A video uploaded to YouTube shows an early AMD’s Mantle API demo that was recorded at the recent APU 2013 developer conference. The demo, done by Oxide Games, shows a game engine (in its alpha state) specifically built for AMD’s Mantle running an increasingly intensive scene.

During the demo, which starts at 25:40, we see a bustling space battle taking place. It’s full of ships, lasers, lights, reflections, and anything else you could imagine that would stress a system’s CPU and GPU. The only problem is, the system remains butter-smooth during the entire demo. Bear in mind this is an R9-290X and an FX-8350, but even with specs like that it’s impressive to see the system appear to keep up regardless of what’s added to the scene.

Mantle slide.

Mantle publicly demoed at APU 2013

Mantle heavily reduces the CPU’s workload

As the speaker discloses after the demo (at 37:18), their CPU is actually hardly even being used. The developer presented the audience with a before-and-after frame analysis of how Mantle affects the system’s workload in comparison to DirectX. In the frame analysis taken from the game running with DirectX, we see a chunk of the CPU being used by the driver thread. In the second (the one where Mantle was used), that thread is simply gone.

Not only did it free up a lot of CPU time when switched to Mantle, but Mantle itself took only a fraction of CPU time to function as opposed to DirectX’s required driver thread. This means that developers have the option to go one of two ways if they use Mantle: they can utilize that unused CPU time to improve their game, or they can simply drop the CPU requirement. The viability of lower CPU performance requirements was later verified even further (at 39:55) when the speaker disclosed that even when underclocked to 2GHz, the FX-8350 was still waiting for the GPU to finish on any given frame. Typically, we would see things the other way around.

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Duplicating Results – Will we see this elsewhere?

It’s really hard to say for certain, but things are really looking up for Mantle. Before this point, the world hasn’t seen a single Mantle demo. Digital Illusions CE (the developer of the popular Battlefield series and Frostbite engine) has already disclosed that they will be developing Battlefield 4 and the upcoming Star Wars: Battlefront for Mantle, but neither have publicly shown gameplay yet.

It’s also worth mentioning that this is only the beginning. The speaker mentions at 41:00, their engine, Mantle, and the hardware being used are all in their early stages. There’s much more optimization to be done in this case, and it’s likely that the larger studios that have also announced support for Mantle have made further progress than Oxide has. It’s hard to say how much further, but it makes sense that a massive game studio would make further progress in these past few months following the Mantle developer kit releases than a smaller group like Oxide.

Does this mean I need an AMD card or AMD CPU?

Absolutely not. Mantle is an open platform. NVidia and Intel both have the freedom to adopt GPU support for it as well. If the launch of these Mantle-enabled titles goes as well as we can expect, there’s a fair chance they’ll both be scrambling to adopt it (if they haven’t already done so behind closed doors). As for the CPU side of things, it appears that Mantle is not only very light on the CPU, but it’s brand-agnostic as well. After the demo, the speaker talks about the game being ran on an i7 chip as well as the 8350.

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Video below, demo starts at 25:40

AMD Mantle API ‘Oxide Games Nitrous’ Slides:

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