06-14-2015, 07:45 AM
Your motherboard likely doesn't support using all of the slots at once. Many boards we've tested in the past only support 4 GPUs. Other possible issues: you do not have enough PCI-e lanes on the CPU and your board doesn't have a PLX chip; you do not have 64-bit PCI-e addressing enabled in the BIOS, or your BIOS does not support 64-bit PCI-e addressing.