Played around quite extensively with g3.ini today.
http://www.rpgwatch.com/wikka/Gothic3IniFiles is pretty much dead on as far as what to tweak. I have read that Gothic 3 will really not access over 2GB RAM so those cache settings should be fine.
I also tried out some of the ideas here:
http://forum.jowood.com/showthread.php?t=126976
Most of them are fine tuning what the RPG wiki summarizes, but the last page has the a good settingwhich differs from the RPGWatch Wiki page:
ObjectDetails.fScreenObjectDistanceCulling_High=0. 004
Curious to see how these tweaks hold true once we have CP 1.7.
Also, as a final test once everything was tweaked ... I was curious to see what my bottleneck is.
I figured it would be my GPU, but it is my Q9300! This particular chip is not a beast of a clocker as it has a really low 7.5x multiplier, but I'm pretty sure 2.75GHz is doable. I tested this out watching CPU core load and GPU load. One of the 4 cores was >90% most of the time, but the GPU was never above 50%! I take this to mean I can go to the Catalyst Control Center and crank up more of the goodies there!
This game does not take advantage of multiple cores, so a duo that can hit 3.6GHz has a much better chance to push the G3 engine to the max.