Only 3/4 Graphics Card detected: GTX 1060 RIG.

[distinct_user]

I just set-up my rig last night. Only 4 GPUs for now. Booted fine and installed Windows 10 Pro x64 with the cards installed.

All cards are brand new.
All drivers have been updated. (Using GeForce experience.)

-Motherboard: ASRock H81 Pro BTC R2.0 (UEFI driver 1.20)
-4x GTX 1060 6GB (3 MSI Gaming X // 1 Inno3D Gaming OC)

Issue is, 3 are detected and 1 isn't. (I think it's the Inno3D one. However, it is on and fans are spinning all the time, non stop on the Inno3D 1060.)

It is only showing 3 cards in CPU-Z, MSI Afterburner, GeForce Experience and even NiceHash.

However, it shows 4 GTX 1060 6GB in devices, but one of them is greyed out (hidden).

[Vann]

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

[distinct_user]

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.

[GaryH]

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

[themurph2k]

Just curious, why must Windows be installed in UEFI mode?