D3D Rightmark
Again, isolating the 6-series boards from the X800s, we see that the GT has little problem keeping up with the Ultra, with the plain 6800 seeing roughly the same performance delta compared to the Ultra that the Radeon X800s experience.
The GT and Ultra experience good shader-based fillrate scores, compared to the Radeons, with the plain 6800 besting the X800 PRO in those cases.
You can also see the effect on geometry performance that the 6800's one less vertex shader unit has.
