MacPro 5,1No Video in Windows(New GPU)

[EmployeeViolator]

Hello. I am new to the forums and I've got a problem: I bought a Sapphire Pulse RX 580 a week ago, I installed it and was able to use it in High Sierra. When I tried to boot into my separate windows 10 drive that I used prior to GPU upgrade, I would not get any video output from my Mac. Again, just fine in OS X, boot in windows 10- no video. I pulled RX 580 out and put my old ATI HD 5870 and both windows and MacOS work. Tried to reinstall windows from USB using HD 5870, but no luck.
Any ideas?
Thanks.

 

[drac]

Start initially with only one screen attached. Have you tried different video outputs.
They may not all work for the login screen.
2ndly if the drivers are not up to date you may be better changing the driver to Microsoft basic display adapter with the old card in then removing the old drivers. Shutting down and restarting to check it works ok. Then shutting down again and swapping card. It it works download the newer version of the driver and do a clean install.
As you know the card works this sounds like a driver/ config issue.

On another point I’m not sure your login is truly necessary.

 

[orph]

may be worth booting with old card then using Display Driver Uninstaller (DDU) then shutting down installing new card and see what happens.

if it works then grab the new drivers

 

[EmployeeViolator]

Nope. Just reinstalled windows 10 using HD5870 works fine with it installed. The device manager says that "basic display driver (Microsoft)" is installed. Then I plug my RX580 in and no video... again. I Even put it in 2nd upper x16 PCIe slot and used 580's 2nd HDMI out this time.
I don't have a monitor and I'm using a JVC 32" TV with HDMI. I plug HD5870 uing DVI out and plug it in tv with DVI to HDMI adapter, works fine in both OSs.
I used Amazon basics HDMI with Ethernet 15ft cable for RX580. I tried the same DVI to HDMI adapter for rx580 and got High Sierra seceen but it was purplish color. In windows I didn't get any out put at all.
Another interesting thing I found that if I have both drives in and choose to boot in windows 1 time (using bootmaneger software from macrumors forums) it restarts, chimes, no video, then white screen and I back in High Sierra.

 

[h9826790]

If you already tried reinstall Windows 10 with HD5870, why not just re-install Windows 10 with just the RX580?

https://forums.macrumors.com/thread...ut-a-boot-screen.2114788/page-9#post-26689280

 

[EmployeeViolator]

Thank you! It is working now. Sort of, I use bootmaneger (program for booting into windows from OS X) and it boot right back to OS X when I choose to boot to Windows. Anyways, that's not a problem at all. The Important thing is that it's working. Thank you again, people of Macrumors forum. Thank you!