RX 560 & RX 570 POST Conflict

[Collider]

I have a setup with RX 570 & RX 560 GPUs. The problem is that 1 / 3 times RX 560 will not be detected and when booted into Windows RX 560 cannot be seen. Then just by rebooting it becomes visible. Seems completely at random. I have tried other RX 560 & RX 570 cards to rule out possibility of hardware issue - it does not seem to be a hardware problem.

I have a motherboard that tells me which PCI-E slots / GPU's are detected during POST, so I can see the 560 not detected even before Windows boots - so it's not a software problem.

What I think might be happening is that the BIOS for 560 is a bit different from 570 and it gets detected a bit slower then 570 - not sure about this one, just a guess.

Is there anything that I can try to get 560 to play nice with 570?

 

[LTC8K6]

Power supply marginal?

 

[alexruiz]

If the RX 560 is powered by the PCI-slot, that is the problem.
PCI-e slots are limited to 75W total, and while that is enough for the RX560 on its own, once you add the RX 570, whatever minimal power RX 570 s taking form the PCI-e slot is enough to cause problems with the RX 560.
Ironically, an RX 560 that takes external power would be the solution.

 

[Collider]

If the RX 560 is powered by the PCI-slot, that is the problem.
PCI-e slots are limited to 75W total, and while that is enough for the RX560 on its own, once you add the RX 570, whatever minimal power RX 570 s taking form the PCI-e slot is enough to cause problems with the RX 560.
Ironically, an RX 560 that takes external power would be the solution.

Thank you, that makes sense.

In my use case I am using powered PCI-E risers with external power, there's a dedicated PCI-E power cable going to the riser itself, I believe it handles ~150W, so should be plenty for RX560.

Still trying to solve this..