Re: GeForce FX 5950 and Source DX 9 performance...
Its not a engin bug. The DX9 path is very heavy in DX9 shaders. The 5XXX FX is much slower in DX9 shaders then the ATI 95XX and up. Most of the DX9 games out now have littil DX 9 shaders so the proformans hit is not to bad on the 5XXX FX cards but Source is heavy use of DX9 shaders so the 5XXX FX speed will be slow and thats why the defalt setting is DX8 path for the 5XXX FX
Now the 6XXX FX is another story and should be fast in the DX9 path.