What's new in DX 9.0c


This year the latest in the DirectX API is getting a bit of a face lift. The new feature in DirectX 9.0c is the inclusion of Pixel Shader and Vertex Shader 3.0. Rather than calling this DirectX 9.1, Microsoft opted to go for a more "incremental" looking update. This can end up being a little misleading because whereas the 'a' and 'b' revisions mostly extended and tweaked functionality, the 'c' revision adds abilities that are absent from its predecessors.

Pixel Shader 3.0 (PS3.0) allows shader programs of over 65,000 lines and includes dynamic flow control (branching). This revision also requires that compliant hardware offer 4 Multiple Render Targets (MRT's allow shaders to draw to more than one location in memory at a time), full 32-bit floating point precision, shader antialiasing, and a total of ten texture coordinate inputs per pixel.

The main advantage here is the ability for developers to write longer, more complex, shader programs that run more efficiently. The flow control will give developers the freedom to write more intuitive code without sacrificing efficiency. Branching allows a shader program the expanded ability to make decisions based on its current state and inputs. Rather than having to run multiple shaders that do different things on different groups of pixels, developers can have a single shader handle an entire object and take care of all its shading needs. Our example of choice will be shading a tree: one shader can handle rendering the dynamics of each leaf, smooth new branches near the top, rugged old bark on the trunk, and dirty roots protruding from the soil.

Vertex Shader 3.0 extends its flow control ability by adding if/then/else statements and including the ability to call subroutines in shader programs. The instruction limit on VS3.0 is also extended to over 65000. Vertex textures are also supported, allowing more dynamic manipulation of vertices. This will get even more exciting when we make our way into the next DirectX revision which will allow for dynamic creation of vertices (think very cool particle systems and hardware morphing of geometry).

One of the coolest things that VS3.0 offers is something called instancing. This functionality can remove a lot of the overhead created by including multiple objects based on the same 3d model (these objects are called instances). Currently, the geometry for every model in the scene needs to be setup and sent to the GPU for rendering, but in the future developers can create as many instances of one model as they want from one vertex stream. These instances can be translated and manipulated by the vertex shader in order to add "individuality" to each instance of the model. To continue with our previous example, a developer can create a whole forest of trees from the vertex stream of one model. This takes pressure off of the CPU and the bus (less data is processed and sent to the GPU).

Now that we've seen what developers are looking at with DirectX 9.0c, let's take a look at how NVIDIA plans to bring these features to the world.
Index NV40 Under the Microscope
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  • TrogdorJW - Wednesday, April 14, 2004 - link

    There are a few things I take away from all the previews of the 6800 Ultra.

    One is that ATI is going to be hard pressed to actually top it. Both will have 16x1 designs, but I don't think ATI will have the 32x0 option, which might be important for games with lots of shadows. (I believe the ATI cards are going to be around 180 million transistors, which leads me to believe that they will not have quite as many features.) I also doubt that ATI will actually support fp32 this time around, which aces DX9.0c/PS3 support from them. That may or may not really matter.

    The next thing is sort of related to the first point: Nvidia now has more features that ATI, but there are still some bugs to work out. DX9 games that were optimized for NV3x seem to be dropping quality on the 6800U. Hopefully the fix to use fp32 instead of fp16 will be both easy and not result in a major performance drop. We'll have to wait and see, though. Other sites have shown quite a few areas that need driver revs, but that's nothing new. At least with NVidia, I feel confident their driver team will fix any major issues and probably increase performance a decent amount as well.

    I also agree with someone else that said the previews might be lower clocked than the final release. First, the RAM is spec'ed for 600 MHz, which makes it odd that they're running at 550 MHz. They may not hit 600, but 575 or maybe 585 seems likely (or at the very least that should be an OC'ing option). The core is currently at 400 MHz, and I think they might be able to bump that up a bit more, but 222 million transistors at .13 micron might not go much higher. We'll have to see what some of the shipping cards from GB, A-bit, Asus, etc. offer in terms of OC'ing headroom, as they might offer better cooling solutions.

    Related to the heat and clockspeed, I'm a little shocked at the heatsink/fan design. If they're going to all the trouble of having a huge HSF, I can't see any reason to not switch the direction it blows and have the Ultra version vent the hot air outside the case. Maybe noise was the reason, or component placement, but I would really prefer to have anything that size making use of external venting. It would be like having your power supply sucking air into the case instead of blowing out... Sure, it might cool the PS better, but the case temp would jump dramatically.

    My final thought is that it will be very interesting to see what sort of price and performance can be had from the regular 6800 cards, and even the 6800XT. I didn't think there would be a "soft-mod" option for Nvidia this round, but it appears I was wrong. Unless NVidia has some way of preventing this from being done. Regardless, if the 6800U is going to start at $500 and the 6800 will go for $300, we could be looking at a 6800XT for $200 or so. It should also have at least the performance of the 5950U, and most likely better.

    Incidentally, I'm betting the mid-range cards (i.e. 6500 or 6600 or whatever) will not really be that great, though, as they'll likely trim them down to 2 or 4 vertex pipelines and 4 or 8 pixel pipelines, so they'll end up looking like something inbetween the 5700U and the 5900XT. And don't look for help from ATI here, as the X300 and X600 look to be renamed 9600SE and 9600XT parts, respectively (a la the Radeon 9000 to 9200 line).
    Reply
  • IamTHEsnake - Wednesday, April 14, 2004 - link

    Whoops! The Radeon 9800 xt only scored 6138 while NV40 scored 12350+ in 3DMark'03. That Ladies and Gentlemen is 2x as many points! Reply
  • IamTHEsnake - Wednesday, April 14, 2004 - link

    Wow I read the review and all I can say is WoW. I read somewhere else that this card scored 12250+ in 3dMark'03 while the 9800 xt scored 8350 on the same system, same set-up. From one generation to the next 33% increase is not bad. not bad at all.


    Come on ATi! I'm rootin' for you!!!
    Reply
  • Schadenfroh - Wednesday, April 14, 2004 - link

    what mobo and mobo drivers were used? i hear that the nforce2 provides an unfair performance advantage for nvidia, even tho the ati should run at the same speed as on a differant motherboard, nvidia just gets an extra boost Reply
  • Warder45 - Wednesday, April 14, 2004 - link

    I want to see the multimedia bench's. Hopefully another article with AMD vs Intel. Reply
  • AlexWade - Wednesday, April 14, 2004 - link

    The thing is freakin' huge! I'm willing to bet dollars-to-doughnuts that ATI's new card isn't the size of a football. Even if this huge beast tops in performance, the extra 20 pounds rules out LAN parties.

    I'll admit, the performance is great. But if ATI is smaller and performs near, or slightly below, then that is the one to buy.
    Reply
  • AlexWade - Wednesday, April 14, 2004 - link

    The thing is freakin' huge! I'm willing to bet dollars-to-doughnuts that ATI's new card isn't the size of a football. Even if this huge beast tops in performance, the extra 20 pounds rules out LAN parties.

    I'll admit, the performance is great. But if ATI is smaller and performs near, or slightly below, then that is the one to buy.
    Reply
  • Reflex - Wednesday, April 14, 2004 - link

    Personally I'll wait to see the budget line on these, I refuse to spend more than $200 on a video card. Chances are I'll end up going Ati however, the 2D video quality is just noticably better, and most of my time on my PC is spent reading, not gaming.

    Oh well, at least the gamers can be happy again. Too bad the AGP slot is not at the bottom of the motherboard, could build some interesting external vented cases if the card could stick that fan outside the case. ;)
    Reply
  • Reliant - Wednesday, April 14, 2004 - link

    Any ideas how the Non Ultra version will perform? Reply
  • Reliant - Wednesday, April 14, 2004 - link

    Any ideas how the Non Ultra version will perform? Reply

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