(too avoid confusion you may not want to read this and just stick with wolfe's, and go to the line below all this stuff.)ok, so the pci-e x16 slot is what the gfx card is plugged into. now the x16 is the bandwidth, like it can do 16mb/s (way higher, just an example), x8 would be 8mb/s and same for x4, on motherboards both pci slots run off of 1 chip, so the 970 has access to doing x16 and x4, no higher or lower, while the 990fx can do either x16/x16 or x16/x8, ther are other options and models but we're just going with these 2 cuz it's giuving me a headache too, and you want it to either be x16 or x8 because the graphics card itself is really running on something closer to x9, so x8 is almost full speed, and x16 gives it full speed ahead.
his appeared after i posted, and his is much simpler.