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
The Current State of DirectX 12 & WDDM 2.0
Although DirectX 12 is up and running in the latest public release of Windows 10, it and many of its related components are still under development. Windows 10 itself is still feature-incomplete, so what we’re looking at here today doesn’t even qualify as beta software. As a result today’s preview should be taken as just that: an early preview. There are still bugs, and performance and compatibility is subject to change. But as of now everything is far enough along that we can finally get a reasonable look at what DirectX 12 is capable of.
From a technical perspective the DirectX 12 API is just one part of a bigger picture. Like Microsoft’s last couple of DirectX 11 minor version upgrades, DirectX 12 goes hand-in-hand with a new version of the Windows Display Driver Model, WDDM 2.0. In fact WDDM 2.0 is the biggest change to WDDM since the driver model was introduced in Windows Vista, and as a result DirectX 12 itself represents a very large overhaul of the Windows GPU ecosystem.
Top: Radeon R9 290X. Bottom: GeForce GTX 980
Microsoft has not released too many details on WDDM 2.0 so far – more information will be released around GDC 2015 – but WDDM 2.0 is based around enabling DirectX 12, adding the necessary features to the kernel and display drivers in order to support the API above it. Among the features tied to WDDM 2.0 are DX12’s explicit memory management and dynamic resource indexing, both of which wouldn’t have been nearly as performant under WDDM 1.3. WDDM 2.0 is also responsible for some of the baser CPU efficiency optimizations in DX12, such as changes to how memory residency is handled and how DX12 applications can more explicitly control residence.
The overhauling of WDDM for 2.0 means that graphics drivers are impacted as well as the OS, and like Microsoft, NVIDIA and AMD have been preparing for WDDM 2.0 with updated graphics drivers. These drivers are still a work in progress, and as a result not all hardware support is enabled and not all bugs have been worked out.
| DirectX 12 Support Status | ||||
| Current Status | Supported At Launch | |||
| AMD GCN 1.2 (285) | Working | Yes | ||
| AMD GCN 1.1 (290/260 Series) | Working | Yes | ||
| AMD GCN 1.0 (7000/200 Series) | Buggy | Yes | ||
| NVIDIA Maxwell 2 (900 Series) | Working | Yes | ||
| NVIDIA Maxwell 1 (750 Series) | Working | Yes | ||
| NVIDIA Kepler (600/700 Series) | Working | Yes | ||
| NVIDIA Fermi (400/500 Series) | Not Active | Yes | ||
In short, among AMD and NVIDIA their latest products are up and running in WDDM 2.0, but not on all of their earlier products. In AMD’s case GCN 1.0 cards are supported under their WDDM 2.0 driver, but we are encountering texturing issues in Star Swarm that do not occur with GCN 1.1 and later. Meanwhile in NVIDIA’s case, as is common for NVIDIA beta drivers they only ship with support enabled for their newer GPUs – Kepler, Maxwell 1, and Maxwell 2 – with Fermi support disabled. Both AMD and NVIIDA have already committed to supporting DirectX 12 (and by extension WDDM 2.0) on GCN 1.0 and later and Fermi and later respectively, so while we can’t test these products today, they should be working by the time DirectX 12 ships.
Also absent for the moment is a definition for DirectX 12’s Feature Level 12_0 and DirectX 11’s 11_3. Separate from the low-level API itself, DirectX 12 and its high-level counterpart DirectX 11.3 will introduce new rendering features such as volume tiled resources and conservative rasterization. While all of the above listed video cards will support the DirectX 12 low-level API, only the very newest video cards will support FL 12_0, and consequently be fully DX12 compliant on both a feature and API basis. Like so many other aspects of DirectX 12, Microsoft is saving any discussion of feature levels for GDC, at which time we should find out what the final feature requirements will be and which (if any) current cards will fully support FL 12_0.
Finally, with Microsoft’s announcement of their Windows 10 plans last month, Microsoft is also finally clarifying their plans for the deployment of DirectX 12. Because DirectX 12 and WDDM 2.0 are tied at the hip, and by extension tied to Windows 10, DirectX 12 will only be available on Windows 10. Windows 8/8.1 and Windows 7 will not be receiving DirectX 12 support.
| DirectX 12 Supported OSes | ||||
| Will Support DX12? | Required WDDM Version | |||
| Windows 10 | Yes | 2.0 | ||
| Windows 8.1 | No | N/A | ||
| Windows 8 | No | N/A | ||
| Windows 7 | No | N/A | ||
Backporting DirectX 12 to earlier OSes would require backporting WDDM 2.0 as well, which brings with it several issues due to the fact that WDDM 2.0 is a kernel component. Microsoft would either have to compromise on WDDM 2.0 features in order to make it work on these older kernels, or alternatively would have to more radically overhaul these kernels to accommodate the full WDDM 2.0 feature set, the latter of which is a significant engineering task and carries a significant risk of breaking earlier Windows installations. Microsoft has already tried this once before in backporting parts of Direct3D 11.1 and WDDM 1.2 to Windows 7, only to discover that even that smaller-scale project had compatibility problems. A backport of DirectX 12 would in turn be even more problematic.
The bright side of all of this is that with Microsoft’s plans to offer Windows 10 as a free upgrade for Windows 7/8/8.1 users, the issue is largely rendered moot. Though DirectX 12 isn’t being backported, Windows users will instead be able to jump forward for free, so unlike Windows 8 this will not require spending money on a new OS just to gain access to the latest version of DirectX. This in turn is consistent with Microsoft’s overall plans to bring all Windows users up to Windows 10 rather than letting the market get fragmented among different Windows versions (and risk repeating another XP), so the revelation that DirectX 12 will not get backported has largely been expected since Microsoft’s Windows 10 announcement.
Meanwhile we won’t dwell on the subject too much, but DirectX 12 being limited to Windows 10 does open up a window of opportunity for Mantle and OpenGL Next. With Mantle already working on Windows 7/8 and OpenGL Next widely expected to be similarly portable, these APIs will be the only low-level APIs available to earlier Windows users.
Facebook
Twitter
RSS
245 Comments
View All Comments
ObscureAngel - Saturday, February 7, 2015 - link
Ryan can you do an article demonstrating the low performance of AMD GPUs in low end CPUs like i3 or anything, in more CPU Bound games comparing to nvidia GPUs in the same CPUs?Unworthy websites have done it, like GameGPU.ru or Digital foundry.
They don't have so much expression because well, sometimes they are a bit dumb.
I confirmed that recently with my own benchmarks, AMD GPUs really have much less performance in the same CPU (low-end CPUs) than an nvidia GPU.
If you look into it and publish maybe that would put a little pressure on AMD and they start to look into it.
But not sure if you can do it, AMD gives your website AMD GPUS and CPUs to benchmark, i'm pretty sure AMD wouldn't like to read the truth..
But since Futuremark new 3dmark is close to release that new benchmark that benchmarks overhead/drawcalls.
It could be nice to give a little highlight of that problem with AMD.
Many people are starting to notice that problem, but AMD are ignoring everyone that claims the lack of performance, so we need somebody strong like Anandtech or other website to analyse these problems and publish to everyone see that something is wrong.
Keep in mind that AMD just fixed the frametime problem in crossfire, cause one website (which i dont remember) publish that, and people start to complain about it, and they start to fix it, and they really fix it.
Now, we already have the complains but we dont have the upper voice like you guys.
okp247 - Sunday, February 8, 2015 - link
Sorry, my bad. The numbers I've stated in the above posts were indeed from either the Follow or Attract scenario.So what is up with the underutilized AMD cards? Clearly, they are not stretching their legs under DX11. In the article you touch upon the CPU batch submission times, and how these are taking a (relatively) long time on the AMD cards. Is this the case also with other draw-call heavy games or is it a fluke in Star Swarm?
ObscureAngel - Monday, February 9, 2015 - link
It happens on games too.I did a video and everything about it.
Spread the word, we need to get AMD attention for this..Since they dont answer me i decided to publicly start to say bad things about them :D
https://www.youtube.com/watch?v=2-nvGOK6ud8
killeak - Saturday, February 7, 2015 - link
Both API (D3D12 and Mantle) are under NDA. In the case of D3D12, in theory if you are working with D3D12 you can't speak about it unless you have explicit authorization from MS. The same with Mantle and AMD.I hope D3D12 goes public by GDC time, I mean the public beta no the final version, after that things will change ;)
Klimax - Saturday, February 7, 2015 - link
Thanks for numbers. They show perfectly how broken and craptastick entire POS is. There are extreme number of idiocies and stupidities in it that it couldn't pass any review by any competent developer.1)Insane number of batches. You want to have at least 100 objects in one to actually see benefit. (Civilization V default settings) To see quite better performance I would say at least 1000 objects to be in one. (Civilization V test with adjusted config) Star Swarm has between 10 to 50 times more batches then Civilization. (Precise number cannot be said as I don't have number of objects to be drawn reported from that "benchmark")
2)Absolutely insane number of superfluous calls. Things like IASetPrimitiveTopology are called (almost) each time an object is to be drawn with same parameters(constants) and with large number of batches those functions add to overhead. That's why you see such large time for DX11 draw - it has to reprocess many things repeatedly. (Some caching and shortcuts can be done as I am sure NVidia implemented them, but there are limits even for otherwise very cheap functions)
3)Simulation itself is so atrociously written that it doesn't really scale at all! This is in space, where number of intersection is very small, so you can process it at maximum possible parallelization.
360s run had 4 cores used for 5,65s with 5+ for 6,1s in total. Bad is weak word...
And I am pretty sure I haven't uncovered all. Note: I used Intel VTune for analysis 1 year ago. Since then no update came so I don't think anything changed at all... (Seeing those numbers I am sure of it)
nulian - Saturday, February 7, 2015 - link
The draw calls are misused on purpose in this demo to show how much better it has become. The advantage for normal games is they can do more light and more effects that use a lot of draw calls without breaking the performance on pc. It is one of the biggest performance different between console and PC draw calls.BehindEnemyLines - Saturday, February 7, 2015 - link
Or maybe they are doing that on purpose to show the bottleneck of DX11 API? Just a thought. If this is a "poorly" written performance demo, then you can only imagine the DX12 improvements after it's "properly" written.Teknobug - Saturday, February 7, 2015 - link
Wasn't there some kind of leaked info that DX12 was basically a copy of Mantle with DX API? Wouldn't surprise me that it'd come close to Mantle's performance.dragonsqrrl - Sunday, February 8, 2015 - link
Right, cause Microsoft only started working on DX12 when Mantle was announced...bloodypulp - Sunday, February 8, 2015 - link
You're missing the point. Mantle/D12 are so similar you could essentially call DX12 the Windows-only version of Mantle. By releasing Mantle, AMD gave developers an opportunity to utilize the new low-level APIs nearly two years before Microsoft was ready to release their own as naturally it was tied to their OS. Those developers who had the foresight to take advantage of Mantle during those two years clearly benefited. They'll launch DX12-ready games before their competitors.