Yes, I guess this would be true, but I wasn't 100% sure

No changes in the BIOS help, tested on the original BIOS F4 and F5.
Success is 3 correct boot but the fourth time error 94/96.
I don't know if this is normal but in the case of Windows8 I can not turn off CSM. After setting disable automatically the option will be enabled.

We will not think of anything anymore?
So I'll buy a WD SN520 drive that works correctly on this board.
Evidently this set cannot work properly.

Windows8 setting would automatically do that if you have secure boot disabled, or one of the other things I mentioned set to Legacy

Some setting I assume, sorry I can't test this myself here and help you to figure it out. I could buy one of those NVME no problem, and already have the SX8200 one, but I can't afford to buy one of these X79 boards (even if they were still selling for $200 which they are not)

Please email Gigabyte and have them test X79S-UP5 + SX6000 and separate test with SX8200, they will do it and send you image of testing results, or a fixed BIOS with images of success once they sort it out.

I bought the PNY XLR8 CS3030 drive, everything is O.K for 30 computer turns on :)
Evidently that combination did not like.
Today I will put the system on a new disk but on a converted BIOS, it will boot from another disk without any problems.
Thank you guys for help, I hope I won't have to add anything to this topic :)

I'm not convinced that Gigabyte will take care of my problem ... So I will sell the disk and buy the SX8200pro for testing.