[Wine] ati and nvidia, why the difference?

[drumstyx]

so I just switched my old geforce 8600 in for my  HD 4850, and it really is a waste of a good card. I'm just wondering if anyone really knows a definitive reason why my awesome ati card gave me 1-6 fps and my relatively old nvidia card is giving me 60+ (practically windows speeds)? Also if anyone knows if there's headway being made on this, that'd be interesting too, i'd love to be able to at some point switch my ATI card back in.