When I insert GTX 1080 on a motherboard, I get the following error:

After Google, I get the solution:

Please change your BIOS settings: BIOS > Advanced > PCIe/PCI/PnP Configuration > Above 4G Decoding and set it to Enabled.

From the link https://www.supermicro.com/support/faqs/faq.cfm?faq=15556