I have 1 RX580, 5 RX570s and I just purchased 7 new RX 5700 XTs. I have the ASRock H110 BTC+ motherboard that has 13 PCI slots on it. 2x 1000 watt PSUs. I'm trying to install Windows 10 and/or Ubuntu. I can get the 7 5700s working ok, even mining. I can get Win10 to recognize the 7 5700s and, once, I got the 7 5700s plus the 580 recognized under Win10. I then tried to add a 570 and it fails with an error. I removed the 570 and then the 580 started failing. If I try the 570 in another machine, it works fine. The mobo bios is up to date with 1.60. I've tried several versions of AMD drivers with the latest GA as my latest attempt. Under Ubuntu, I've tried Ubuntu 20.04 and 18.04. I've tried 20.20, 20.30 and 20.40 AMD drivers under 18.04. I've tried 20.20, 20.30 and 20.45 drivers under Ubuntu 20. Nothing seems to be real stable.
Am I missing something or is this something that's just not possible? I'd like to mine with it but I also have other GPU software I develop and I need to test. Any and all help would be appreciated.