Tahiti: The First Direct3D 11.1 GPU

One of the many changes coming in Windows 8 next year will be the next iteration of Direct3D, which will be Direct3D 11.1. More so than any other version of Direct3D so far, D3D11.1 is best summed up as a housekeeping release. There will be some new features, but compared to even past point releases such as 10.1 and 9c it’s a small release that’s going to be focusing more on improving the API itself – particularly interoperability with SoC GPUs for Windows 8 – than it will be about introducing new features. This is largely a consequence of the growing length of time for all matters of development hardware and software. By the time Windows 8 ships Direct3D 11 will be 3 years old, but these days that’s shorter than the development period for some AAA games. Direct3D 11/11.1 will continue to be the current Windows 3D API for quite some time to come.

With regards to backward compatibility in D3D11.1, there’s one new feature in particular that requires new hardware to support it: Target Independent Rasterization. As a result AMD’s existing D3D11 GPUs cannot fully support D3D11.1, thereby making Tahiti the first D3D 11.1 GPU to be released. In practice this means that the hardware is once again ahead of the API, even more so than what we saw with G80 + D3D10 or Cypress (5870) + D3D11 since D3D11.1 isn’t due to arrive for roughly another year. For the time being Tahiti’s hardware supports it but AMD won’t enable this functionality until the future – the first driver with D3D11.1 support will be a beta driver for Windows 8, which we expect we’ll see for the Windows 8 beta next year.

So what does D3D11.1 bring to the table? The biggest end user feature is going to be the formalization of Stereo 3D support into the D3D API. Currently S3D is achieved by either partially going around D3D to present a quad buffer to games and applications that directly support S3D, or in the case of driver/middleware enhancement manipulating the rendering process itself to get the desired results. Formalizing S3D won’t remove the need for middleware to enable S3D on games that choose not to implement it, but for games that do choose to directly implement it such as Deus Ex, it will now be possible to do this through Direct3D.

S3D related sales have never been particularly spectacular, and no doubt the fragmentation of the market is partially to blame, so this may be the push in the right direction that the S3D market needs, if the wider consumer base is ready to accept it. At a minimum this should remove the need for any fragmentation/customization when it comes to games that directly support S3D.

With S3D out of the way, the rest of the D3D11.1 feature set isn’t going to be nearly as visible. Interoperability between graphics, video, and compute is going to be greatly improved, allowing video via Media Foundation to be sent through pixel and compute shaders, among other things. Meanwhile target independent rasterization and some new buffer commands should give developers a few more tricks to work with, while double precision (FP64) support will be coming to pixel shaders on hardware that has FP64 support.

Finally, looking at things at a lower level D3D11.1 will be released alongside DXGI 1.2 and WDDM 1.2, the full combination of which will continue Microsoft’s long-term goal of making the GPU more CPU-like. One of Microsoft’s goals has to been to push GPU manufacturers to improve the granularity of GPU preemption, both for performance and reliability purposes. Since XP things have gotten better as Vista introduced GPU Timeout Detection and Recovery (TDR) to reset hung GPUs, and a finer level of granularity has been introduced to allow multiple games/applications to share a GPU without stomping all over each other, but preemption and context switches are still expensive on a GPU compared to a CPU (there are a lot of registers to deal with) which impacts performance and reliability.

To that end preemption is being given a bit more attention, as WDDM 1.2 will be introducing some new API commands to help manage it while encouraging hardware developers to support finer grained preemption. Meanwhile to improve reliability TDR is getting a major addition by being able to do a finer grained reset of the GPU. Currently with Windows 7 a TDR triggers a complete GPU reset, but with Windows 8 and WDDM 1.2 the GPU will be compartmentalized into “engines” that can be individually reset. Only the games/applications using a reset engine will be impacted while everything else is left untouched, and while most games and applications can already gracefully handle a reset, this will further reduce the problems a reset creates by resetting fewer programs.

 

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  • Ryan Smith - Thursday, December 22, 2011 - link

    Yep. Still working on it. Hold tight Reply
  • MadMan007 - Thursday, December 22, 2011 - link

    Np, just not used to seeing incomplete articles publsihed on Anandtech that aren't clearly 'previews'...wasn't sure if you were aware of all the missing stuff. Reply
  • DoktorSleepless - Thursday, December 22, 2011 - link

    Crysis won't be defeated until we're able to play at a full 60fps with 4x super sampling. It looks ugly without the foliage AA. Reply
  • Ryan Smith - Thursday, December 22, 2011 - link

    I actually completely agree. That's even farther off than 1920 just with MSAA, but I'm looking forward to that day. Reply
  • chizow - Thursday, December 22, 2011 - link

    Honestly Crysis may be defeated once Nvidia releases its driver-level FXAA injector option. Yes, FXAA can blur textures but it also does an amazing job at reducing jaggies on both geometry and transparencies at virtually no impact on performance.

    There's leaked driver versions (R295.xx) out that allow this option now, hopefully we get them officially soon as this will be a huge boon for games like Crysis or games that don't support traditional AA modes at all (GTA4).

    Check out the results below:

    http://www.hardocp.com/image.html?image=MTMyMjQ1Mz...
    Reply
  • AnotherGuy - Thursday, December 22, 2011 - link

    If nVidia released this card tomorrow they woulda priced it easily $600... The card succeeds in almost every aspect.... except maybe noise... Reply
  • chizow - Thursday, December 22, 2011 - link

    Funny since both of Nvidia's previous flagship single-GPU cards, the GTX 480 and GTX 580, launched for $499 and were both the fastest single-GPU cards available at the time.

    I think Nvidia learned their lesson with the GTX 280, and similarly, I think AMD has learned their lesson as well with underpricing their HD 4870 and HD 5870. They've (finally) learned that in the brief period they hold the performance lead, they need to make the most of it, which is why we are seeing a $549 flagship card from them this time around.
    Reply
  • 8steve8 - Thursday, December 22, 2011 - link

    waiting for amd's 28nm 7770.

    this card is overkill in power and money.
    Reply
  • tipoo - Thursday, December 22, 2011 - link

    Same, we're not going to tax these cards at the most common resolutions until new consoles are out, such is the blessing and curse of console ports. Reply
  • CrystalBay - Thursday, December 22, 2011 - link

    Hi Ryan , All these older GPUs ie (5870 ,gtx570 ,580 ,6950 were rerun on the new hardware testbed ? If so GJ lotsa work there. Reply

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