Only the GeForce cards can be tested with AO enabled because the feature has been implemented through the GeForce drivers and is not an option in the Radeon drivers. Let's see what this subtle image-quality enhancement feature costs in terms of performance.
Compared to the High Detail performance on the previous page, the AO feature has almost cut performance in half. At this resolution, this result isn't as bad as it sounds because all of these cards were performing at ridiculously high frame rates anyway. But this doesn't bode well for the AO feature as the resolution increases.
Indeed, at 1680x1050, we're seeing a crack in the GeForce 9600 GT's armor. It's still playable with a minimum frame rate of 30 FPS, but the card's prospects for 1920x1200 aren't looking good.
At the 1920x1200 resolution, the GeForce 9600 GT is still mostly playable, even though the minimum frame rate has gone down to 24 FPS. All of the other GeForce cards are demonstrating a little more oomph and smoother performance.
Wow! The AO feature doesn't combine with the 2560x1600 resolution very well at all, pulling the GeForce 9600 GT and GeForce 8800/9800 GT below 20 FPS minimum. Even the GeForce GTS 250's minimum frame rate is brought down below 30 FPS, leaving the GeForce GTX 260 as the only card we tested that is able to handle the AO feature at 2560x1600 with a minimum frame rate above 30 FPS.