you just have to enable the 4g decoding when u add more than 4 gpu
okay thanks
want to know if it makes a differece x16 x8 or x4
x1, x4, x8, x16, whatever, is fine for the purposes of the card attached to that slot. The difference in speed between x1 and x16 is negligible for mining purposes.
However, trying to have all the physical x16 slots to run at x16 may cause you to run out of PCIe lanes, depending on how your chipset and CPU allocate them. (The idea is to have *some* resources allocated for all devices somehow, even at reduced bus speeds, but this doesn't always occur automatically; unfortunately it's a rather finicky process.)