I have 8500GT and its really lame but my GF have perfomance about 40% less than you and i still play LFS ~60fps when alone on track and unfortunatelu, 15 AL cars and fps 20 its what i get with all maxed out . Online its better.all maxed out +AAfull +AF16 and still can play usualy at 60~30 fps unless there is bariers
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thuse things cut my perfomance.
I think that your settings is to fault.
If you could wright all your settings from NVidia panel like AA, AF, Vsync, threading and stuff here i could look into it and maybe ill advice something becouse a used to have problem like this with games but i spend some time reading what settings do what and after spending 15 minutes mesing with settings my games where at last playable
Sry 4 my english, is lam3 but hope you will understand me
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.