My rig's symptoms are as follows:
1. If two RX 580 plugged directly on MOBO, works fine under Claymore ETH+SIA dual mode
2. If one RX 580 plugged via USB PCIe riser, works fine under Claymore ETH+SIA dual mode
3. If two RX 580 plugged via USB PCIe risers, works fine under Claymore ETH single mode
4. If two RX 580 plugged via USB PCIe risers, reboots after a few seconds under Claymore ETH+SIA dual mode
5. If three RX 580 plugged via USB PCIe risers, reboots after a few seconds under Claymore ETH single mode
In conclusion, only one card with dual mode or two cards with ETH single mode will work, other situations never work.
I even tried SimpleminingOS, still no luck, if two RX 580 are plugged via USB PCIe risers, after I launch Claymore, it will only run for a few seconds then the screen goes black and reboot immediately.
My hardware specs:
PSU: LEPA G1600-MA 1600W
VGA: XFX RX 580
VGA Driver: Crimson ReLive Edition 17.6.1
MOBO: Asus PRIME Z270-A
MOBO BIOS VERSION: PRIME Z270-A BIOS 0906
CPU: Intel Celeron G3900
HDD: Sandisk SDSA6PM-064G 64G m.2 SSD
RAM: Crucial CT4G4DFS8213 4GB 288-Pin DDR4
USB PCIe Riser: VER006C
Case: Rosewill L4500
My bios settings: 4G decoding on
I think the issue is not about the PSU, because my PSU is 1600W, which is enough for two cards.
Also, If all seven Rx 580 are plugged via risers, Windows 10 can recognize seven cards, but claymore still runs for a few seconds then reboot immediately.
https://pbs.twimg.com/media/DCA2MVgVoAAVPcd.jpghttps://pbs.twimg.com/media/DCA2N01UQAAuZel.jpg