So I have this board and had been having problems with anymore than 4 GPU's. But I now have it running with 6 NV GPU's with the IGD as the display output.
I'm running with Kabylake i3-7300 so having that is not a problem and you don't need to be looking at Skylake parts. I do have a Skylake G3900 which actually had more issues.
The main thing is to set all your settings in BIOS first and then install Windows 10, I had an old image of Windows 10 I was using that just would not boot when you enabled 'Above 4G Decoding'.
I didn't need to change much in BIOS using latest 7977v1E BIOS.
1. Above 4G Decoding 'Enabled'
2. Win 8.1/10 set to 'Enabled'
3. UEFI only
Hopefully this helps, and clears up issues for some or at least provides some hope.
Its on MSI Z170A GAMING M5 s1151 ?
Because i try almost everything Expect instal Windows only on UEFI settings but it will help ?
My succes was when i turn on once 5 GPU but with only 0 Mhm and sometimes it was 2 Mhm
:/