Is the inability to disable CSM on Windows 10 motherboards affecting Fast Startup?

The Biostar B85 motherboard paired with a GTX770 graphics card runs Windows 10 (UEFI + GPT partitioning). The system still performs a self-test at startup and cannot enable Fast Startup. The CSM option in the BIOS is enabled; attempting to disable it results in an error. Sub-options (e.g., Boot Device Control) have been changed to UEFI mode, but the “Video Policy” setting cannot be switched to UEFI mode, preventing CSM from being fully disabled. Seeking specific configuration adjustments.