Problem to setup my rig with more then 2 video cards

Hi,
I startet last Monday with my first rig with Hive OS. These are my components:
MSI B450 GAMING PLUS MAX 7B86-016R
AMD RYZEN 3 2200G YD2200C5FBBOX
CORSAIR SERIES RM1000X CP-9020094-EU
8GB CORSAIR DDR4-2133 CMV8GX4M1A2133C15
WD GREEN SSD 3D NAND WDS120G2G0A 120GB
2 x GIGABYTE GeForce RTX 2060 OC 6G 2.0
1 x Zotac GeForce RTX 3070 Twin Edge OC White Edition 8GB
3 x KOLINK PCI-E 1x to 16 x Powered Riser

With to 2 cards in any combination the rig is mining stable. But when I put into the 3rd card without any bios configuration, it’s ignored by the mainboard.

For this problem I found already the bio configuration “Above 4G Decoding”. After enabling it, I reboot with 2 cards. > Everything was fine. Then I tried to add the 3rd card, but the rig didn’t came up again. That means it’s starts to boot, but the screen stays black.

I removed all 3 cards and reset the BIOS. > PC works fine. > enabled “Above 4G Decoding” and reboot> PC works fine > added first card and reboot> PC works fine > added 2nd card and reboot> PC works fine > added 3rd card and reboot> PC didn’t come up again

Is there any other BIOS configuration, what I have missed there?
Are the cards not compatible? (I can’t imagine this :wink: )
Are there any other ideas for a solution?

Thanks for some tips

Just a quess, refer to your mb manual, sounds like mb issue for sure. do u have separate power source to each gpu? check risers, maybe try to switch from working card to that 3. gpu and boot up. good luck

all gpu’s have separate power source from the power adapter installed.
I also connect molex from power adapter to each the riser card.

have u tried to change riser from working card to non working, or tried with one gpu that is working and replace the other working one to that same riser with your new one and try with that two gpu setup?
How abou riser connector on that new gpu,to pci-e, take a close look that all the contact surfaces are intact without any damage…missing a bit of contact surface etc.Its not rare that even new risers can be faulty

All components were ok. So updated the Bios of the MSI Mainboard to version “7B86vHB”. This solve the problem. So thanks for support!