Quote from: distinct_user on July 02, 2017, 01:16:09 PM

Quote from: Vann on July 02, 2017, 11:24:41 AM

Try setting the PCI-E slots to GEN 2 or GEN 1 in the Bios. Also make sure the PCI-E 4-pin power connectors are plugged in to the motherboard and see if Windows is installed in UEFI mode.

How to test whether Windows 10 was installed with UEFI?

https://superuser.com/questions/946868/how-to-test-whether-windows-10-was-installed-with-uefi

I changed to gen 2 and all 4 are now appearing. It was in Auto prior.

However, the 4th GPU is coming up with Code 43 in Device Manager. I don't understand what you mean.

I just installed Windows 10 Pro via a USB from boot and installed it on my SSD.

what he's saying is if Win 10 was not installed in UEFI mode, it will not see/work with all the GPUs in the system. If it's not a UEFI install you will have to reformat and reinstall Win 10 in UEFI mode. To find out if your Win 10 is in UEFI mode, following the instructions in his link listed above: https://superuser.com/questions/946868/how-to-test-whether-windows-10-was-installed-with-uefi