The DirectX 12 Performance Preview: AMD, NVIDIA, & Star Swarm
by Ryan Smith on February 6, 2015 2:00 PM EST- Posted in
- GPUs
- AMD
- Microsoft
- NVIDIA
- DirectX 12
About a year and a half ago AMD kicked off the public half of a race to improve the state of graphics APIs. Dubbed "Mantle", AMD’s in-house API for their Radeon cards stripped away the abstraction and inefficiencies of traditional high-level APIs like DirectX 11 and OpenGL 4, and instead gave developers a means to access the GPU in a low-level, game console-like manner. The impetus: with a low-level API, engine developers could achieve better performance than with a high-level API, sometimes vastly exceeding what DirectX and OpenGL could offer.
While AMD was the first such company to publicly announce their low-level API, they were not the last. 2014 saw the announcement of APIs such as DirectX 12, OpenGL Next, and Apple’s Metal, all of which would implement similar ideas for similar performance reasons. It was a renaissance in the graphics API space after many years of slow progress, and one desperately needed to keep pace with the progress of both GPUs and CPUs.
In the PC graphics space we’ve already seen how early versions of Mantle perform, with Mantle offering some substantial boosts in performance, especially in CPU-bound scenarios. As awesome as Mantle is though, it is currently a de-facto proprietary AMD API, which means it can only be used with AMD GPUs; what about NVIDIA and Intel GPUs? For that we turn towards DirectX, Microsoft’s traditional cross-vendor API that will be making the same jump as Mantle, but using a common API for the benefit of every vendor in the Windows ecosystem.
DirectX 12 was first announced at GDC 2014, where Microsoft unveiled the existence of the new API along with their planned goals, a brief demonstration of very early code, and limited technical details about how the API would work. Since then Microsoft has been hard at work on DirectX 12 as part of the larger Windows 10 development effort, culminating in the release of the latest Windows 10 Technical Preview, Build 9926, which is shipping with an early preview version of DirectX 12.
GDC 2014 - DirectX 12 Unveiled: 3DMark 2011 CPU Time: Direct3D 11 vs. Direct3D 12
With the various pieces of Microsoft’s latest API finally coming together, today we will be taking our first look at the performance future of DirectX. The API is stabilizing, video card drivers are improving, and the first DirectX 12 application has been written; Microsoft and their partners are finally ready to show off DirectX 12. To that end, today we’ll looking at DirectX 12 through Oxide Games’ Star Swarm benchmark, our first DirectX 12 application and a true API efficiency torture test.
Does DirectX 12 bring the same kind of performance benefits we saw with Mantle? Can it resolve the CPU bottlenecking that DirectX 11 struggles with? How well does the concept of a low-level API work for a common API with disparate hardware? Let’s find out!
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loguerto - Saturday, February 7, 2015 - link
Microsoft is on the right way, but still, Mantle is the boss!FXi - Saturday, February 7, 2015 - link
I'm sadly more curious as to whether the 6 core chips prove their worth. A lot of rumor guessing seems to think that DX12 might finally show that a 6 core matters, but nothing here shows that. That's a very key issue when it comes to whether to go for a higher end chip or stick with the 4 core cpu's.GMAR - Saturday, February 7, 2015 - link
Excellent article. Thank you!Shahnewaz - Saturday, February 7, 2015 - link
Wait a minute, isn't the GTX 980 a 165W TDP card? Then how is it pulling over 200 watts?eRacer1 - Sunday, February 8, 2015 - link
The GTX 980 isn't pulling over 200W. The numbers shown are system power consumption not video card power consumption. The GTX 980 system power consumption isn't unusually high.Also, the system power consumption numbers are understating the power difference between the GTX 980 and Radeon 290X cards themselves under DX12. The GTX 980 has such a large performance advantage over the 290X in DX12 that the CPU is also using more power in the GTX 980 system to keep up with the video card.
If anything the 290X power consumption is "too low", especially under DX12. To me it looks like the GPU is being underutilized, which seems to be the case based on the low FPS results and power consumption numbers. That could be due to many reasons: poor driver optimization, 290X architectural limitations, benchmark bug or design choice, Windows 10 issue, 290X throttling problem, etc. Hopefully, for AMD's sake, those issues can be worked out before the Windows 10 launch.
Shahnewaz - Sunday, February 8, 2015 - link
That doesn't explain the <20W difference in both systems.And it's not like the CPU usage is also radically different.
Remember, the TDP difference between the GPUs is a massive 165W (290W vs 165W).
eRacer1 - Sunday, February 8, 2015 - link
"That doesn't explain the <20W difference in both systems. And it's not like the CPU usage is also radically different."Looking at the CPU usage graphs in the review the GTX 980 DX12 CPU average across all four cores is about 80% while the 290X average is only about 50%. So the GTX 980 CPU is doing 60% more work. That alone could easily account for 20+W watts of extra power consumption on CPU in the GTX 980 system. The ~60% CPU higher usage in the GTX 980 system makes sense as the frame rate is 56% higher as well. So what looks like a 14W difference is probably more like a 35W difference between the GTX 980 and 290X video cards.
But the 35W difference doesn't tell the whole story because the GTX 980 is also 56% faster while using less power. So the GTX 980 has a MASSIVE efficiency advantage under these benchmark conditions. And it is doing it within a reasonable TDP because by the time you back out all of the non-GPU power consumption (CPU, memory, motherboard, hard drive, fans, etc.) and PSU inefficiency losses from the 271W system power consumption you'd likely find that the GTX 980 is under 200W.
So the question we are left with is why is a 290W TDP 290X system power consumption only 285W under DX12? By the time you subtract the CPU power consumption (which is somewhat less than that of the GTX 980 test due to only being at 50% load instead of 80%), motherboard, memory and other components the 290X is probably using only 200-220W. To me it looks like the 290X is being bottlenecked and as a result isn't using as much power as one would expect. What the source of the bottleneck is, and if it is correctable, remains a mystery.
Shahnewaz - Saturday, February 7, 2015 - link
It looks like AMD GPUs will get some 400%+ performance improvements! Sick!ET - Sunday, February 8, 2015 - link
My main takeaway from the article is that NVIDIA has done a much better job of optimising its DX11 drivers. AMD needs low level badly.bloodypulp - Sunday, February 8, 2015 - link
They already have it: Mantle.