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 - Friday, September 12, 2003 - link

    I think the insinuation is clear from that nVidia email posted and Gabe's comments. Valve believed nVidia was trying to "cheat" with their D50s by intentionally having fog disabled etc. Rather than toss around accusations, it was simpler for them to just require that the benchmarks at this point be run with released drivers and avoid the issue of currently bugged drivers with non-working features, whether the reason was accidental or intentional.

    Considering that the FXes fared poorly with 3DMark and again with HL2 - both using DX9 implementations, I think it might be fair to say that the FXes aren't going to do too much better in the future. Especially considering the way they reacted to 3DMark 03 - fighting the benchmark rather than releasing drivers to remedy the performance issue.

    I'd like to see how the FXes do running HL2 with pure DX8 rather than DX9 or a hybrid, as I think most people owning current nVidia cards are going to have to go that route to achieve the framerates desired.
  • Anonymous User - Friday, September 12, 2003 - link

    I dont see how the minimum requirements set but valve are going to play this game. 700mhz and a TNT2. The FX5200's could barely keep up.
  • Anonymous User - Friday, September 12, 2003 - link

    #68: 33 fps * 1.73 = 57.09 fps (add the one to account for the intial 33 score).

    This doesn't quite work out based on the 57.3 score of the 9800 Pro so corrected score on the Nvidia was probably closer to this:
    57.3 / 1.73 = 33.12 fps

    #69: I would definitely try to find a 9600 Pro before I bought a 9500 Pro. The 9600 fully supports DX9 whereas the 9500 does not.
  • Anonymous User - Friday, September 12, 2003 - link

    Guess Its time to upgrade...
    Now where's my &*&%%'n wallet!!


    Wonder where I'll be able to find a R9500Pro (Sapphire)
  • Anonymous User - Friday, September 12, 2003 - link

    The performance increase between the FX5900 and Rad9800Pro is not 73%. Do the math correctly and it turns into 36.5% lead. The article should be revised.
  • atlr - Friday, September 12, 2003 - link

    If anyone sees benchmarks for 1 GHz computers, please post a URL. Thanks.
  • WooDaddy - Friday, September 12, 2003 - link

    Hmmm... I understand that Nvidia would be upset. But it's not like ATI is using a special setting to run faster. They're using DX9.. Nvidia needs to get on the ball. I'm going to have to upgrade my video card since I have a now obsolete Ti4200 GF4.

    GET IT TOGETHER NVIDIA!!! DON'T MAKE ME BUY ATI!

    I might just sell my Nvidia stock while I'm at it. HL2 is a big mover and I believe can make or break the card on the consumer side.
  • Anonymous User - Friday, September 12, 2003 - link

    I had just ordered a 5600 Ultra thinking it would be a great card. It's going back.

    If I can get full DX 9 performance with a 9600 Pro for around $180, and that card's performance is better than the 5900 Ultra - then I'm game.

    I bought a TNT when Nvidia was making a name for it's self. I bought a GF2 GTS when Nvida was destroying the 3dfx - now Nvidia seems to have droped the ball on DX9. I want to play HL2 on what ever card I buy. A 5600 ultra won't seem to cut it. I know the 50's are out there, but I've seen the Aquamark comparision with the 45's and 50's and I'm not impressed.

    I really wanted to buy Nvidia, but I cannot afford it.

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

    #62: I do have the money but I choose to spend it elsewhere. FYI: I spend $164 US on my 2.4C and I'm running speeds faster than the system used for this benchmark.

    "The Dell PCs we used were configured with Pentium 4 3.0C processors on 875P based motherboards with 1GB of memory. We were running Windows XP without any special modifications to the OS or other changes to the system."

    Anand was using a single system to show what HL2 performance would be on video cards available on the market today. If we was to run benchmarks on different CPU's he would have to spend a tremendous amount more time doing so. In the interest of getting the info out as soon as possible, he limited himself to a single system.

    I would deduce from the performance numbers of HL2 in Anand's benchmarks that unless you have a 9600 Pro/9800 Pro, your AMD will not be able to effectively run HL2.
  • Anonymous User - Friday, September 12, 2003 - link

    Woohoooo!!!
    My ATI 9500@9700 128MB with 8 pixel pipelines and 256bit access beats the crap out of any FX.
    And it only costed me 190euros/190dollars

    Back to the drawing board NVidia.
    Muahahahah!!!

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