those of you having trouble with getting more than 2 GPU's working on the Asus Prime H270-PLUS - follow these instructions and you can upgrade to 8 GPU's no problem...

the issue is the bios & drivers are not going to support more than 2 or 3 GPU's unless you update them

1st, update BIOS to the latest version

2nd, go to Asus.com and look up the H270-PLUS and find the latest VGA driver  (while you're there you might as well download all the drivers and make sure you're running the latest, chipset, audio, lan, etc..)

once you download the VGA driver, extract the file in windows, then run it.... let it update your VGA driver

Now go in to BIOS change the M.2 to PCI-E if you have the M.2 to PCI-E adapters installed

Go to Advanced > System Config or whatever it's called > turn 4g decoding ON

(you may need to install 1st GPU in the pci-express x16 slot before turning 4g decoding ON)

Then > DIM > change speed to GEN 1

All the others (PEG, PCH) put on Auto...

This seems to do the trick... also, i am not sure if it will install all GPU's if you plug them all in at the same time - i just go 1 by 1, that way i know if i need to replace a bad riser etc..

Hope this helps...