All of the tests were run at 1600 x 1200, a resolution that both of these cards happen to handle quite well across all games. Our testing yielded the following conclusions:
# Half Life 2 is about 10% faster on the X800 XL than on the 6800GT (based on an average of our 5 demos). However, the other Source engine based game in our suite, Vampire: The Masquerade - Bloodlines, shows the two GPUs performing rather similarly. With only two Source engine based titles, we cannot extrapolate any further based on these results, but they are interesting nonetheless. We will add that although the average frame rates were similar, the minimum frame rates were higher on the X800 XL than on the 6800GT in Vampire. There wasn't a huge difference, but enough to be noticeable during gameplay.
# Under Doom 3, the 6800GT is just under 30% faster than the X800 XL, a huge win for NVIDIA.
# Need for Speed Underground 2 has some serious issues on the 6800GT as it is almost 40% slower than on the X800 XL. While the X800 XL will play NFSU2 quite well at 1600 x 1200 with all of the details turned all the way up (AA off however), the 6800GT cannot. To have a $400 card and not be able to play the latest games at 1600 x 1200 at the highest detail settings is unacceptable in our opinion. This is an area to which NVIDIA needs to pay closer attention.
# Far Cry and Halo both favor the 6800GT with advantages of 12.5% and 10% respectively.
# The five remaining games basically performed identically on the X800 XL and on the 6800GT.
