More on Mixed-Mode for NV3x

We briefly mentioned the Mixed Mode of operation for NV3x GPUs that Valve implemented in Half-Life 2, but there is much more to it than just a special NV3x code path. In fact, the mixed mode NV3x code path was really only intended for the GeForce FX 5900 Ultra (NV35). The mainstream FX chips (5200/5600) require a slightly different code path.


Here you can see the 40% performance boost NVIDIA gets from the special NV3x code path.

The GeForce FX 5600 (NV31) uses a code path that is internally referred to as dx82; this path is a combination of DX9 (pixel shader 2.0) and DX8.1 (pixel shader 1.4) code, and thus, doesn't look as good as what you'll see on the 5900 Ultra.

Although the 5900 Ultra performs reasonably well with the special NV3x mixed mode path, the 5600 and 5200 cards do not perform well at all. Valve's recommendation to owners of 5600/5200 cards is to run the DX8 (pixel shader 1.4) code path in order to receive playable performance under Half-Life 2. The performance improvement gained by dropping to the DX8 code path is seen most on the GeForce FX 5200; although, there is a slight improvement on the 5600 as you can see below:

The sacrifices that you encounter by running either the mixed mode path or the DX8 path are obviously visual. The 5900 Ultra, running in mixed mode, will exhibit some banding effects as a result of a loss in precision (FP16 vs. FP32), but still looks good - just not as good as the full DX9 code path. There is a noticeable difference between this mixed mode and the dx82 mode, as well as the straight DX8 path. For example, you'll notice that shader effects on the water aren't as impressive as they are in the native DX9 path.

Are the visual tradeoffs perceptive? Yes. The native DX9 path clearly looks better than anything else, especially the DX8.0/8.1 modes.

Improving Performance on NVIDIA The Test
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  • Anonymous User - Sunday, September 14, 2003 - link

    Umm.. could you PLEASE not use shockwave for those
    tables? Our firewalls & browser configs also won't let it through, so these reviews become pretty much useless to read.
  • Anonymous User - Sunday, September 14, 2003 - link

    where are the benchmarks comparing HL2 at different CPUs? I mean, i obviously know I'm gonna have to upgrade my gf3 to a new card (first game to make me even think of that... didnt care for ut2k3), but what about my venerable athlon xp 1800+ ? :(
  • Anonymous User - Saturday, September 13, 2003 - link

    #98, look at the 9700 Pro numbers, subtract 4-5%.

    Still, if I were to see another set of benchmarks, I'd DEFINITELY want these:

    GeForce4 MX440 OR GeForce2 Ti - As an example of how well GF2/GF4MX cards perform on low detail settings, being DX7 parts.
    GeForce3 Ti200 OR GeForce3 Ti500 - It's a DX8 part, and still respectably fast; lots of people have Ti200s, anyway.
    GeForce4 Ti4200 - This is an incredibly common and respectably fast card, tons of people would be interested in seeing the numbers for these.
    GeForce FX 5600 Ultra - Obvious.
    GeForce FX 5900 Ultra - Obvious.
    Radeon 8500 - It's still a good card, you know.
    Radeon 9500 Pro - Admit it, you're all interested.
    Radeon 9600 Pro - Obvious.
    Radeon 9700 vanilla - Because it would show how clock speed scales, and besides these (and softmodded 9500s) are quite common.
    Radeon 9700 Pro - Obvious.
    Radeon 9800 Pro - Obvious.

    The GeForce FX 5200 and GeForce4 Ti4600 might be nice too, but the Radeons 9000 through 9200 would be irrelevant (R200-based).

    Also, obviously, I'd like to see them on two or three different detail levels (preferably three), to show how well some of the slower ones run at low detail and see how scalable Source really is. Speaking of scalability, a CPU scaling test would be extremely useful as well, like AnandTech's UT2003 CPU scaling test.

    This sort of thing would probably take a lot of time, but I'd love to see it, and I bet I'm not alone there. I think something like what AnandTehc did with UT2003 would be great.

    Just my ~$0.11.
  • clarkmo - Saturday, September 13, 2003 - link

    I can't believe the Radeon 9500 hacked to a 9700 wasn't included in the benchmarks. What was he thinking? I guess Anand didn't have any luck scoring the right card. There are some still available, you know.
  • Anonymous User - Saturday, September 13, 2003 - link

    Quote from the Irari information minister:
    "Nvidia is kicking ATI's butt. Their hardware is producing vastly superior numbers."
  • Anonymous User - Saturday, September 13, 2003 - link

    Nvidia quote: "Part of this is understanding that in many cases promoting PS 1.4 (DirectX 8) to PS 2.0 (DirectX 9) provides no image quality benefit."

    3Dfx said some years ago that no one ever would use or notice the benefits of 32 bit textures. Nvidia did and 3Dfx is gone. Will Nvidia follow the 3Dfx path?
  • Anonymous User - Saturday, September 13, 2003 - link

    Anyone remember when ati.com sold rubber dog crap?
  • Pete - Saturday, September 13, 2003 - link

    #74, straight from the horse's mouth:

    http://www.nvnews.net/#1063313306
    "The GeForce FX is currently the fastest card we've benchmarked the Doom technology on and that's largely due to NVIDIA's close cooperation with us during the development of the algorithms that were used in Doom. They knew that the shadow rendering techniques we're using were going to be very important in a wide variety of games and they made some particular optimizations in their hardware strategy to take advantage of this and that served them well. --John Carmack"

    Of course those D3 numbers were early (as are these HL2 ones), so things can change with updated drivers.
  • Anonymous User - Saturday, September 13, 2003 - link

    I don't know if it has already been asked, but even if it has I ask again for emphasis.

    Anand, it would be nice if you could add a 9600 non-pro bench to the results. You mention raw GPU power being the determining factor now, and as the 9600 Pro's difference in memory clock is more significant than its engine clock, it would be interesting and informative to the budget/performance croud to note the 9600 non-pro performance in HL2.

    Thanks for all your informative, insightful, accurate, in-depth articles.
  • Anonymous User - Friday, September 12, 2003 - link

    I always find it interesting how people say ATI is the "little guy" in this situation.

    ATI has been a major player in the video card market since the eighties (I had a 16-bit VGA Wonder stuck in an 8-bit ISA slot in an 8088/2 system) and that didn't change much even when 3dfx came onto the scene. A lot of those voodoo pass through cards got their video from an ATI 3d expression or some other cheap 2d card (Cirrus Logic or Trident anyone?).

    Nvidia and ATI have been at each others throats ever since Nvidia sold its first video card on the OEM market. 3dfx was just a little blip to ATI, Nvidia stealing away a bunch of its OEM sales with a bad 2d/good 3d video card on the other hand, well, that was personal.

    I imagine someone at ATi saying something like this:

    "All of you guys working on making faster DACs and better signal quality are being transferred to our new 3d department. Its sort of like 2d cept its got one more d, thats all we know for right now.".

    ATI knows how to engineer and build a video card, they have been doing it for long enough. Same with Matrox (Matrox builds the Rolls Royce's of video cards for broadcast and video editing use), Nvidia on the other hand knew how to build 3d accelerators, and not much else. The 2d on any early Rage card slaughtered the early Nvidia cards.

    Course, the 3d sucked balls, thats what a Canopus Pure 3d was for though.

    Now ATI has the whole "3d" part of the chip figured out. The driver guys have their heads wrapped around the things as well (before 3d cards came around ATI's drivers were the envy of the industry). Its had many years of experience dealing with games companies, OS companies, standards, and customers. And its maturity is really starting to show after a few minor bumps and bruises.

    ATI wants its market back, and after getting artx it has the means to do it. Of course, Nvidia is going to come out of this whole situation a lot more grown up as well. Both companies are going to have to fight blood tooth and nail to stay on top now. If they don't Matrox might just step up to the plate and bloody both of their noses. Or any of those "other" long forgotten video card companies that have some engineers stashed away working on DX 7 chips.

    God knows what next month is going to bring.

    Anyways, sorry for the rant..

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