PCIE question/Issue

Hi

I have a Z97X-Gamning 5 board and have 4 GPU (HD7970) running nicely in x16 slot and the 3 x1 slots in Utbutu 14.04

Problem is when I add a 5th GPU to PCIE x4 it turns off the x1 slots I know that but cant seem to over ride it in the BIOS, but when I add another GPU to the remaining x8 slot the machine wont boot.

Any pointers...

Cheers

Rob