What's the impact of having only 8 lanes per video card rather than 16?

I just want to know what the impact of having two graphics cards in sli on a 16 lane motherboard that will split each video card to 8 lanes each. So what is the difference of having 8 lanes to a video card than 16 lanes.



e.g. having two EVGA GTX 580 in sli on a Asus Sabertooth P67, which will split the 16 available lanes to 8 for each v card.|||Not much, only 2-3%, i.e a few frames