Question about MSI RX 470 graphics card and onboard graphics

I have a computer with one MSI Radeon RX 470 card in it. When it is the primary graphics adapter MSI Afterburner can read the settings and I can overclock the memory. I tried enabling the onboard graphics as well for the primary display thinking the RX 470 would hash faster. But when I did this MSI Afterburner could no longer read the settings from the RX 470 and it thought there were four RX 470 GPUs in the computer, when in fact there is only one, and it could not read any of these phantom cards. But Claymore Dual Miner could still see the one RX 470 and it was hashing. In order for MSI Afterburner to be able to read the card and set the memory clock it has to be enabled in the computer bios as the primary adapter. Is this a limitation of the bios on my motherboard? I was hoping to use the onboard graphics to let the RX 470 only mine coins but without being able to overclock the memory with MSI Afterburner I got the same hashing speeds regardless if it was set to primary adapter or not.