1st Ethereum build problem - only recognizing 1 GPU

[bigfoot9]

I'm having trouble with my first build.  For whatever reason the MB will only detect one of my GPU's.  I have 6, and it doesn't matter which I plug into which PCIe slot, only one will get detected.  I have tried plugging each one in individually to test and they all work just fine, tested all slots and they are fine as well.  All AMD cards with driver installed.  Any thoughts? 

Power supply - 1500 watts
MB - Gigabyte Z270P-D3
GPU's - 2 r290, 1 390, 3 480's

Thanks

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[gt_addict]

Have you enabled 4G decoding in the bios? Have you set pcie config to gen1 or gen2?

[bigfoot9]

I was able to change the pcie config, I changed from auto to gen 2.  Apparently this mobo doesn't have a setting to enable 4g decoding.  Bios is up to date.  Any thoughts?

[bigfoot9]

So when I have more than 1 GPU plugged in there is no signal sent out to the monitor... why would that be? 

[bigfoot9]

Any ideas?  Should I just buy a different MB to see if that fixes the issue?