If you have an ASUS Motherboard with UEFI BIOS there is no way you can disable the Intel or AMD Integrated Graphics, however there is a way to specify the primary display. Follow these steps to disable the Onboard Integrated Graphics:
- Enter BIOS Setup.
- Go to Advanced Menu
- Go to Chipset Configuration Menu
- Go to Internal Graphics Menu
- Set the Internal Graphics Mode to Disable or choose PEG/PCI instead of Auto or IGFX. (IGFX means the onboard graphics).
- If you also have a Multi Monitors option set this to disable.