All - The following is my email exchange with ASRock support.  Thought it may be helpful to others.  The 'hack' below did NOT work for me.  I had to roll back to an earlier build AND had to do the hack.

Rig:
H110ProBTC+
Trying to build 12 GPU rig, can only get 7 cards running
8 - 1060 EVGA GTX GPUs
8 GB RAM
Windows 10 Pro 1709

I am still having issues with this motherboard.  I have a somewhat bizarre situation.

Regardless of the number of GPUs I have installed in the MB, device manager throws a code 43 on the 3rd from the bottom in the device manager list.  Meaning, if I have 10 cards installed, the 8th card is not working and shows code 43.  If I only have 6 cards installed, then the 4 the card throws the code.

I've used DDU to uninstall and then reinstall Nvidia's drivers at least 4 times.

Thoughts?

ASRock Support:

This issue is related to newer OS version, Windows 10 RS3 (1709) 16299 build.

If using previous Windows OS version, RS2 (1703) or RS1 (1607), the issue would not exist.

May also try work around with registry trick (see below for detail) to check. Otherwise, please use previous Windows version.

However, we recommend user to use previous Windows 10 version for their system.

 
(work around with regedit) code 12/43

However, may give it a try with registry trick below to check if it worked. Otherwise, please use Windows 10 RS2 or RS1.

Click the Start button, type regedit in the Start Search box, and then click regedit in the Programs list.

User Access Control permission If you are prompted for an administrator password or for confirmation, type the password, or click Continue.

Locate the following registry subkey, and then click it:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\PnP\Pci

If the HackFlags registry entry is not present, follow these steps:

On the Edit menu, point to New, and then click DWORD (32-bit) Value.

Type HackFlags, and then press ENTER.

On the Edit menu, click Modify.

In the Value data box, type 0x600, click Hexadecimal in the Base area, and then click OK.

Exit Registry Editor.

 

If the HackFlags registry entry is present, follow these steps:

Right-click HackFlags, and then click Modify.

In the Value data box, type 0x600, click Hexadecimal in the Base area, and then click OK.

Exit Registry Editor.