I made great progress yesterday and today: phew...
After three weeks of issues and failures : it was crazy for me after spending so much money and time going up the wall ...
But yesterday after the message from
@djlild7hina about issue on Windows too, I planed to resolve the problems or return the Mobo too.
After doing more tests, no problem on Windows but High Sierra was unstable.
There was a fact that my bios clock was always frozen : whatever the real cause: It was sure to be a
First explanation to my problem : yeah : when i removed the battery, weeks ago, to clear CMOS and after putting it back for some reason, it was dead ( amazing on a brand new mobo ...).
So a new CR2032 and lets go...
Second explanation : after clear CMOS a first time I used the Bios Flash Back Button : classic procedure but I remember to use
the Bios renamer [EG R6EE.CAP] instead doing that manually...
This time I reflashed the two bioses but i renamed the bios files manually.
After adjusting the bios settings, tried with macOS Catalina.
And the light has come : I renewed my EFI and my USBmap for iMacPro 1,1 : and at the first attempt , it was done.
Pcie allocation BIOS config: 16x/8x/4x
Slot 1 - RX VEGA 56
Slot 2 - N/A
Slot 3 - RX VEGA 56
Slot 4 - N/A
NVMe location :
M 2_1 socket the lower one : Samsung 970 EVO ( Windows)
M 2_2 socket the top one : WD Black SN750 ( Catalina ---->CC copy from DIMM 2_2)
DIMM 2_1 left : Samsung 970 EVO ( 1TO Data)
DIMM 2_2 right : PNY XLR8 CS3030 ( 250 GB Catalina)
Yes really and no crash no freeze...phew...
Even Aquantia AQC107 10G works.
I will do more test tomorrow. Before calling for RMA.
Happy New Year and all the best for 2021.

View attachment 503602