GeForce Gets Mixed
Mixed mode for NV3X?
What is mixed mode? Well, Valve has reworked the Half-Life 2 engine to help the performance of the GeForce FX cards by trading off texture fetches for pixel shader instruction count and partial-precision registers if the situation calls for it. By doing so, it helped pull NVIDIA-based cards' frame rates.
While showing a very significant increase in frame rates for the FX5900 card, the 5600 and 5200 Ultra gets a slight performance boost. Remember, on the slide in page 1, the FX5900 at full DX9 only clocked in at only about 31 FPS. While it is all well that NVIDIA's performance has increased, these performance gains will be moot as new DX9 functionality will allow for less parital-precision functions.
So how much has Valve done to please its NVIDIA-based video-card-owning customers? It has spent 5 times the amount of time optimizing the NV3X path as they have the DX9 path. Valve themselves were alarmed at the performance difference and went further to say that ATI did not need such specific optimizations performed.
The easy thing for Valve to do ( and to save lots of time ) is to treat NV3X as DX8 hardware, meaning it's up to us gamers to turn on DX9 for the game ourselves. Also, by doing so, if we had DX8 running with GeForce FX 5200/5600, we will get playable framerates. Another downside of having the mixed mode equivalent ( 2 different optimizations ) for any single title will mean that future developers using this engine will have to tailor their code to both paths, which means more budget required, which some studios do not have.