Pci Express lanes and sli

[Nick24]

I am thinking about getting a intel 8700k but it only had 16 pci Express lanes and I have two gtx 970s. So my question is how much of a performance hit will I see in gaming when running both cards at 8x in sli instead of 16x

 

[popatim]

Its very small.

 

[The Paladin]

which motherboard is in question ?