Start working on it:
[GUIDE] Adding Bifurcation Support to ASUS X79 UEFI BIOS - BIOS/UEFI Modding / BIOS Modding Guides and Problems - Win-Raid Forum (level1techs.com)
[Guide] - How to Bifurcate a PCI-E slot - BIOS/UEFI Modding / BIOS Modding Guides and Problems - Win-Raid Forum (level1techs.com)
[Guide] PCIe Bifurcation - mapping IIO/IOU to PCIe slot - BIOS/UEFI Modding / BIOS Modding Guides and Problems - Win-Raid Forum (level1techs.com)
Good luck.