Dual GPU - nvidia on first PCI-e, radeon on the second. It will work?

[adnowa]

Hi,

I would like to run Catalina on my PC but currently I have unsupported GPU GTX 1080. I would like to add a second GPU probably Sapphire RX560 2GB for Catalina. I read a lot about this but still I'm not sure. My motherboard (P8H77-m pro) has one PCI-e 3.0 x16 and second PCI-e 2.0 x4 mode. The second slot has low bandwidth so I need to put 1080 at the first. I'm not sure if it will be a issue if rx560 will be at the second slot? Also I have another doubt. Do I need to unplug monitor from GTX1080 before macOS booting?
Anyone has similar motherboard and run with dual GPU? I'm not sure if my motherboard will be able to handle this correctly so maybe I will need to change it to some Z77

 

[jaymonkey]

I would like to add a second GPU probably Sapphire RX560 2GB for Catalina. I read a lot about this but still I'm not sure. ..... I'm not sure if it will be a issue if rx560 will be at the second slot? Also I have another doubt. Do I need to unplug monitor from GTX1080 before macOS booting?

@adnowa,

A GPU should work in a x4 PCIe slot but the lower bandwidth will hamper the card so it makes sense to put a relatively low performance GPU in there such as a RX 560 ... Note: Do not use XFX RX 560 as its VBIOS is incompatible with MacOS.

You can disable the Nvidia card in MacOS via ACPI calls (custom SSDT or edited DSDT), the process is detailed in @RehabMan's guide linked in this post :-

RehabMan SSDT trick used to disable unsupported Nvidia and keep it in pcie slot while using Mojave

For people like me who want to keep their unsupported videocard in pcie slot 1 (or 2, or 3, I suppose) while testing Mojave with a second supported videocard in another pcie slot (or integrated igpu), take a look at @RehabMan Guide : [FIX] "Window Server Service only ran for 0 seconds" with...

www.tonymacx86.com

You can disable the AMD card in Windows via Device Manager.

If your monitor has enough inputs you can connect both the Nvidia and the GPU at the same time, MacOS will use the AMD GPU (with Nvidia disabled) and Windows will use the Nvidia GPU without you having to unplug any cables, most monitors will automatically switch to the active input ... if your monitor does not support this you will have to use the monitors input select button (or menu option) to select to required input but its still better than having to swap cables around.

This method has been successfully used by many users that have dual (AMD/Nvidia) GPU's in their systems.

Cheers
Jay

 

[adnowa]

Thanks for so specific answer!