DirectX11 Redux

With the launch of the 5800 series, AMD is quite proud of the position they’re in. They have a DX11 card launching a month before DX11 is dropped on to consumers in the form of Win7, and the slower timing of NVIDIA means that AMD has had silicon ready far sooner. This puts AMD in the position of Cypress being the de facto hardware implementation of DX11, a situation that is helpful for the company in the long term as game development will need to begin on solely their hardware (and programmed against AMD’s advantages and quirks) until such a time that NVIDIA’s hardware is ready. This is not a position that AMD has enjoyed since 2002 with the Radeon 9700 and DirectX 9.0, as DirectX 10 was anchored by NVIDIA due in large part to AMD’s late hardware.

As we have already covered DirectX 11 in-depth with our first look at the standard nearly a year ago, this is going to be a recap of what DX11 is bringing to the table. If you’d like to get the entire inside story, please see our in-depth DirectX 11 article.

DirectX 11, as we have previously mentioned, is a pure superset of DirectX 10. Rather than being the massive overhaul of DirectX that DX10 was compared to DX9, DX11 builds off of DX10 without throwing away the old ways. The result of this is easy to see in the hardware of the 5870, where as features were added to the Direct3D pipeline, they were added to the RV770 pipeline in its transformation into Cypress.

New to the Direct3D pipeline for DirectX 11 is the tessellation system, which is divided up into 3 parts, and the Computer Shader. Starting at the very top of the tessellation stack, we have the Hull Shader. The Hull Shader is responsible for taking in patches and control points (tessellation directions), to prepare a piece of geometry to be tessellated.

Next up is the tesselator proper, which is a rather significant piece of fixed function hardware. The tesselator’s sole job is to take geometry and to break it up into more complex portions, in effect creating additional geometric detail from where there was none. As setting up geometry at the start of the graphics pipeline is comparatively expensive, this is a very cool hack to get more geometric detail out of an object without the need to fully deal with what amounts to “eye candy” polygons.

As the tesselator is not programmable, it simply tessellates whatever it is fed. This is what makes the Hull Shader so important, as it’s serves as the programmable input side of the tesselator.

Once the tesselator is done, it hands its work off to the Domain Shader, along with the Hull Shader handing off its original inputs to the Domain Shader too. The Domain Shader is responsible for any further manipulations of the tessellated data that need to be made such as applying displacement maps, before passing it along to other parts of the GPU.



The tesselator is very much AMD’s baby in DX11. They’ve been playing with tesselators as early as 2001, only for them to never gain traction on the PC. The tesselator has seen use in the Xbox 360 where the AMD-designed Xenos GPU has one (albeit much simpler than DX11’s), but when that same tesselator was brought over and put in the R600 and successive hardware, it was never used since it was not a part of the DirectX standard. Now that tessellation is finally part of that standard, we should expect to see it picked up and used by a large number of developers. For AMD, it’s vindication for all the work they’ve put into tessellation over the years.

The other big addition to the Direct3D pipeline is the Compute Shader, which allows for programs to access the hardware of a GPU and treat it like a regular data processor rather than a graphical rendering processor. The Compute Shader is open for use by games and non-games alike, although when it’s used outside of the Direct3D pipeline it’s usually referred to as DirectCompute rather than the Compute Shader.

For its use in games, the big thing AMD is pushing right now is Order Independent Transparency, which uses the Compute Shader to sort transparent textures in a single pass so that they are rendered in the correct order. This isn’t something that was previously impossible using other methods (e.g. pixel shaders), but using the Compute Shader is much faster.



Other features finding their way into Direct3D include some significant changes for textures, in the name of improving image quality. Texture sizes are being bumped up to 16K x 16K (that’s a 256MP texture) which for all practical purposes means that textures can be of an unlimited size given that you’ll run out of video memory before being able to utilize such a large texture.

The other change to textures is the addition of two new texture compression schemes, BC6H and BC7. These new texture compression schemes are another one of AMD’s pet projects, as they are the ones to develop them and push for their inclusion in DX11. BC6H is the first texture compression method dedicated for use in compressing HDR textures, which previously compressed very poorly using even less-lossy schemes like BC3/DXT5. It can compress textures at a lossy 6:1 ratio. Meanwhile BC7 is for use with regular textures, and is billed as a replacement for BC3/DXT5. It has the same 3:1 compression ratio for RGB textures.

We’re actually rather excited about these new texture compression schemes, as better ways to compress textures directly leads to better texture quality. Compressing HDR textures allows for larger/better textures due to the space saved, and using BC7 in place of BC3 is an outright quality improvement in the same amount of space, given an appropriate texture. Better compression and tessellation stand to be the biggest benefactors towards improving the base image quality of games by leading to better textures and better geometry.

We had been hoping to supply some examples of these new texture compression methods in action with real textures, but we have not been able to secure the necessary samples in time. In the meantime we have Microsoft’s examples from GameFest 2008, which drive the point home well enough in spite of being synthetic.

Moving beyond the Direct3D pipeline, the next big feature coming in DirectX 11 is better support for multithreading. By allowing multiple threads to simultaneously create resources, manage states, and issue draw commands, it will no longer be necessary to have a single thread do all of this heavy lifting. As this is an optimization focused on better utilizing the CPU, it stands that graphics performance in GPU-limited situations stands to gain little. Rather this is going to help the CPU in CPU-limited situations better utilize the graphics hardware. Technically this feature does not require DX11 hardware support (it’s a high-level construct available for use with DX10/10.1 cards too) but it’s still a significant technology being introduced with DX11.

Last but not least, DX11 is bringing with it High Level Shader Language 5.0, which in turn is bringing several new instructions that are primarily focused on speeding up common tasks, and some new features that make it more C-like. Classes and interfaces will make an appearance here, which will make shader code development easier by allowing for easier segmentation of code. This will go hand-in-hand with dynamic shader linkage, which helps to clean up code by only linking in shader code suitable for the target device, taking the management of that task out of the hands of the coder.

Cypress: What’s New The First DirectX 11 Games
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  • Qfromchicago - Friday, November 27, 2009 - link

    Windows 7 Profession
    Onkyo 805
    Diamond 5870
    Still no 3rd option for hd audio.

    Has anyone been able to work this thing
  • charme - Friday, November 27, 2009 - link

    same here.
    no 3rd option for hd audio
  • otni - Sunday, November 29, 2009 - link

  • FlyTexas - Saturday, November 14, 2009 - link

    What good does it do to launch this, if there are still none for sale a month later?

    Yes, I know there were a few sold up front, but NewEgg has been out for awhile...
  • RavnosCC - Tuesday, November 17, 2009 - link

    The 57xx series are readily available, they also support HD Audio.
  • RavnosCC - Monday, November 23, 2009 - link

    "As of today, new PowerDVD 9 Ultra customers will receive build 2320, which includes support for HDMI bitstreaming of undecoded (full quality) audio with ATI Radeon 5000 series graphics cards, and the Auzentech X-Fi Hometheater HD sound card. An update patch for current owners of PowerDVD 9 Ultra is scheduled to be available next Friday (11/27).

  • Qfromchicago - Wednesday, November 25, 2009 - link

    Though happy that finally we will get hd audio using powerdvd, but why limit it to new customers only. It seems to me that if you can offer it to new customers, you should be able to offer it to everyone at the same time.
  • Qfromchicago - Sunday, October 18, 2009 - link

    I have win 7, a diamond 5870, powerdvd 9 ultra version 2201 and still I don't get he 3rd choice for the HD audio bitstreaming. Has anyone been able to get bitstreaming to work with powerdvd 9. Thanks
  • RavnosCC - Thursday, November 5, 2009 - link

    UPDATE: Looks like late November for the mythical patch...

    "Hi everyone,
    Yes... we read these forums regularly. Feedback is forwarded to the appropriate people. These forums aren't the best way for us to provide customer support, so if you have an issue, please open a support ticket through our website.

    We can't always comment on new developments... or at least we like to wait until we have a definite answer. I know everyone noticed the reviews for the ATI Radeon 5000 series graphics cards, where certain reviewers were using a pre-release version of PowerDVD 9 to demonstrate HDMI bitstreaming of Blu-ray audio. Support for this feature will be in the next PowerDVD update (patch), which will be available later this month. I don't have a firm date on this, but we're trying to expedite it. Please keep in mind that each of our regular updates includes fixes for new BD titles and new (or forthcoming) hardware / drivers across the PC ecosystem, and so the feature you are anxiously waiting for isn't the only thing that we need to include in the update. Of course, each update has to go through a full quality assurance testing procedure, to make sure that none of the changes introduced any new issues.

    So... sorry for going quiet on you... but I and others read every post in this thread and other relevant threads, following up as needed (in some cases, directly through private messages on these forums).

  • RavnosCC - Wednesday, October 28, 2009 - link

    I am in the same boat, with Vista, I have powerdvd 9 ultra fully patched and still no third option for hi-def passthrough... :-/

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