I ve been trying to solve this issue for two weeks and I am really, really out of ideas ATM. I ve got Asrock B85 Pro4 Mobo, 4 Sapphire Nitro 470 4 GB (not Nitro+), PSU 850P2 EVGA and I cannot get all 4 card to work or even get detected. I do get two cards detected and the third gets detected but reports a problem with drivers (error 43). I ve tried reinstalling different drivers, changed 6 different risers, changed GPU position, setting up one by one, Win 7 or Win 10, it simply wont work. I ve tested all GPUs and all PCI slots, they work independently but just not together. Is there anything in Mobo Bios which might be the issue or anything else which comes to your mind cause I really do not know what else to try.
Any help s appreciated.