Question new build, all is fine except getting both pcie gpu’s to work at same time (non sli)

Jan 12, 2020
Hi all. Long time lurker, first time poster. Built a pc for a friend for day trading, he wants a powerhouse and a 6 monitor setup. Here’s the hardware.

MOBO asrock x570m pro 4
CPU amd ryzen 7 3700x
RAM 64gb ballistix gaming kit
HD sabrent rocket NVMe 4.0 m.2 ssd
GPU1 gigabyte geforce gtx 1660, pcie 3.0x16 (physically has to be installed in pcie_1 slot)
GPU2 msi geforce 210, pcie 2.0x16

Everything setup and installed fine (win 10) with gpu1 in pcie_1 and ssd in m2_1.

I had intended to use gpu1 to feed 4 monitors and onboard graphics to feed the other 2, but that cpu doesn’t allow it... no problem, got a spare geforce 210 that can power 2 monitors.

When I add gpu2 to pcie_3, gpu1 is ignored.

I moved ssd to M2_2... pc works fine with gpu1 in pcie_1. But when I add gpu2 back in, system won’t boot, cant even get to bios.

Looking into bios settings. The manual is absolutely no help here, shows what settings there are, but no explanation about what they do.

Searching online doesn’t quite yield what change I can implement to fix this.

Is anyone able to shed light on this? How can I use both gpu’s at the same time and not bridged, so that I can power 6 monitors with this rig?