Question Pcie lane issue?

Apr 14, 2021
I am trying to run two gpus on the same motherboard but am running into problems, seemingly due to limited pcie lanes.

Specs are

Msi B450 Carbon Gaming pro AC
Ryzen 7 3700x
Corsair Vengeance LPX 64gb (2x32) 2400 CL16 ddr4
MSI rtx 2070 super
Palit rtx 3060

Running the 2070s in either slot on its own boots fine. Running both together with 2070s in main slot works with occasional issues.

Running 3060 in the main slot and 2070 in second slot doesn't boot, ie I get no signal through hdmi.

Main pcie slot is pcie 3.0 x16; second is pcie 2.0 x4.

The 3060 needs a pcie x16 slot to acheive full hashrate when mining which is why I'd like it to have the main slot.

Why won't the 2070s work for display when the 3060 is in the main slot? Is there a work around?

I should note that I don't get signal from the 3060 either when both cards are in.

Thanks for your help!!