Hi
I think we are confusing drives not being detected in the boot menu and drives being detected in the bios.
From the manual for your board.
SATA Power on PORT0~SATA Power on PORT5
Enables or disables each SATA port. (Default: Enabled)
Can you check please in the bios, peripherals group that all the sata ports are enabled.
Here is the board manual link, as you have a later bios the settings may not be the same.
http://download.gigabyte.cn/FileList/Manual/mb_manual_ga-970a-d3p_v.2.x_e.pdfCheck out section 2-5
Seems you can set the power state of each individual Sata port