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

    #61.. i take it YOU have the money to shell out for top of the line hardware ????????? i sure as hell don't, but like #42 said, " more widely used comp "

    i my self am running a 1700+ at 2400+ speeds, no way in hell am i gonna go spend the 930 bucks ( in cdn funds )on a 3.2c P4, thats NOT inc the mobo and ram, and i'm also not gonna spend the 700 cdn on a barton 3200+ either, for the price of the above P4 chip i can get a whole decient comp, may not be able to run halflife at its fullest, but still, i'm not even interested in HL2, it just not the kind of game i play, but if i was, whay i typed above, is still valid..


    anand... RUN THESE HL2 BENCHES ON HARDWARE THE AVERAGE PERSON CAN AFFORD !!!!!!!!!!!!!!!!!!!!!!!! not he spoiled rich kid crap .....
  • Anonymous User - Friday, September 12, 2003 - link

    #42 "...should have benchmarked on a more widely used computer like a 2400 or 2500+ AMD...":

    The use of 'outdated' hardware such as your 2400 AMD would have increased the possibility of cpu limitations taking over the benchmark. Historically all video card benchmarks have used the fastest (or near fastest) GPU available to ensure the GPU is able to operate in the best possible scenario. If you want to know how your 2400 will work with HL2, wait and buy it when it comes out.

    In reference to the 16/32 bit floating point shaders and how that applies to ATI's 24 bit shaders:

    It was my understanding that this quote was referencing the need for Nvidia to use it's 32 bit shaders as future support for its 16 bit shaders would not exist. I don't see this quote pertaining to ATI's 24 bit shaders as they meet the DX9 specs. The chance of future HL2 engine based games leaving ATI users out in the cold is somewhere between slim and none. For an example of how software vendor's react to leaving out support for a particular line of video card, simply look at how much work Valve put into making Nvidia's cards work. If it was feasible for a software vendor to leave out support for an entire line like your are refering to (ATI in your inference) we would have had HL2 shipping by now (for ATI only though...).
  • Anonymous User - Friday, September 12, 2003 - link

    58, http://myweb.cableone.net/jrose/Jeremy/HL2.jpg
  • Anonymous User - Friday, September 12, 2003 - link

    Are pixel shader operations anti-aliased on current generation video cards? I ask because in the latest Half Life 2 technology demo movie, anti-aliasing is enabled. Everything looks smooth except for the specular highlights on the roof and other areas, which are still full of shimmering effects. Just seems a little sore on the eyes.
  • Anonymous User - Friday, September 12, 2003 - link

    An observation:

    Brian Burke = Iraqi Information Officer

    I mean this guy rode 3dfx into the dirt nap and he's providing the same great service to Nvidia.

    Note to self: Never buy anything from a company that has this guy spewing lies.
  • Anonymous User - Friday, September 12, 2003 - link

    OK, this article was great.

    For us freaks, can you do a supplement article. Do 1600x1200 benchmarks!!!

    Things will probably crawl, but it would be nice to know that this should be the worst case at this resolution when ATI and NVidia come out with next gen cards.

    Also, was any testing done to see if the benchmarks were CPU or GPU limited? Maybe use the CPU utilization montior in Windows o see what the CPU thought. maybe a 5.0 GHz processor down the road will solve some headaches. Doubtful, but maybe....
  • Anonymous User - Friday, September 12, 2003 - link

    Whats really funny is that Maximum PC magazine built an $11000 "Dream Machine", using a GeforeFX 5900 and i can built a machine for less then $2000 and beat it using a 9800 pro.

    Long Live my 9500 pro!
  • Anonymous User - Friday, September 12, 2003 - link

    I can play Frozen Throne and I am doing so on a GeForce2MX LOL (on a P2@400mhz).
  • Anonymous User - Friday, September 12, 2003 - link

    look at my #46 posting - i know it's different engines, different API's, different driver revisions etc...
    but still it's interesting..

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

    #52 different engines, different results. hl 2 is probably more shader limited than doom 3. The 9600pro has strong shader performance, which narrows the gap in shader limited situations such as hl 2.

    btw, where did you get those doom 3 results? Only doom 3 benches I know about are based off the old alpha or that invalid test from back when the nv35 was launched...

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