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
Comments Locked

111 Comments

View All Comments

  • Anonymous User - Friday, September 12, 2003 - link

    I perviously posted this in a wrong place so let me just shamelessly repost in here:

    Let me just get my little disclaimer out, before I dive into being a devil's advocate - I own both 9800pro and fx5900nu and am not biased to neither, ATi or nVidia.
    With that being said, let me take a shot at what Anand opted not to speculate about ant that is the question of ATi/Valve colaboration and their present and future relationship.
    First of all, FX's architecture is obviously inferior to R3x0 in terms of native DX9 and tha is not going to be my focus. I would rather debate a little about the business/finacial side of ATi/Valve relationship. That's the area of my expertise and looking at this situation from afinacial angle might add another twist to this.
    What got my attention are Gabe Newell presentations slides that have omitted small but significant things like "pro" behind r9600 and his statement of "optimiztions going too far" without actually going into specifics, other than new detonators don't render fog. Those are small but significant details that add a little oil on a very hot issue of "cheating" in regards to nVidia's "optimizations". But I sopke of inancial side of things, so let me get back to it. After clearly stating how superior ATi's harware is to FX, stating how much effort they have invested to make the game work on FX (which is absolutely commendable) I can not help but notice that all this perfectly leads into the next great thing. A new line of ATi cards will be bundeled with ATi cards (or vice versa), and ATi is just getting ready to offer a value DX9 line. Remember how it was the only area that they have not covered and nVidia was selling truckloads of FX5200 in the meantime. After they have demonstrated how poorly FX flagship performs, let alone the value parts, is't it a perfect lead into selling shiploads of those bundeled cards(games). Add to that Gabe's shooting down of any optimization efforts on nVidia's part (simply insinuate on "chaets") and things are slowly moving in the right direction. And to top it all off, Valve expilcitley said that future additions will not be done for DX8 or so called mixed class but exclusively DX9. What is Joe consumer to do than? The only logical thing - get him/herself one of those bundles.
    That concludes my observations on this angle of this newly emerged attraction and I see only good things on the horizon for ATi stockholders.
    Feel free to debate, disagree and criticize, but keep in mind that I am not defending or bashing anybody, just offering my opinion on the part I considered equally as interesting as hardware performance is.
  • Anonymous User - Friday, September 12, 2003 - link

    Wow...I buy a new video card every 3 years or so..my last one was a GF2PRO....hehe...I'm so glad to have a 9800PRO right now.
    Snif..I'm proud to be Canadian ;-)
  • Anonymous User - Friday, September 12, 2003 - link

    How come the 9600 pros hardly loses any performance going from 1024 to 1280? Shouldn't it be affected by only having 4 pipelines?
  • Anonymous User - Friday, September 12, 2003 - link

    MUHAHAHA!!! Go the 9600pros, i'd like to bitch slap my friends for telling me the 9600's will not run half-life 2. I guess i can now purchase an All-In-Wonder 9600pro.
  • Anonymous User - Friday, September 12, 2003 - link

    Man, I burst into a coughing/laughing spree when I saw an add using nVidia's "The way it's meant to be played" slogan. Funny thing is, I first noticed the add on the page titled "What's Wrong with Nvidia?"
  • Anonymous User - Friday, September 12, 2003 - link

    booyah, i hope my ti4200 can hold me over at 800x600 until i can switch to ATI! big up canada
  • Anonymous User - Friday, September 12, 2003 - link

    You can bet your house nvidia's 50 drivers will get closer performance, but they're STILL thoroughly bitchslapped... Ppl will be buying R9x00's by the ton. Nvidia better watch out, or they'll go down like, whatwassitsname, 3dfx ?
  • dvinnen - Friday, September 12, 2003 - link

    Hehe, I concer. Seeing a 9500on there would of been nice. But I really want to see is some AF turned on. I can live with no AA (ok, 2x AA) but I'll be damn if AF isn't going to be on.
  • Anonymous User - Friday, September 12, 2003 - link

    Anand, you guys rock. It's because of your in depth reviews that I purchased the Radeon 9500 Pro. I noticed the oddity mentioned of the small performance gap between the 9700 Pro and the 9600 Pro at 1280x1024. I would really like to see how the 9500 Pro is affected by this (and all the other benchmarks). If you have a chance, could you run a comparison between the 9500 Pro and the 9600 Pro (I guess what I really want to know if my 9500 Pro is better than a 9600 Pro for this game).

    Arigato,
    The Internal
  • Pete - Friday, September 12, 2003 - link

    (Whoops, that was me above (lucky #13)--entered the wrong p/w.)

Log in

Don't have an account? Sign up now