Currently 5 GPU's on AM4 board - No Problem!
Mobo: ASRock Fatal1ty AB350 Gaming K4 AM4 ATX AMD Motherboard (sweet board I love it so far)
CPU: AMD Ryzen 3 1200 (mining XMR - 175h/s)
Memory: 1 x Corsair Value Select DDR4 - 4GB
GPUs: 5 x RX560 4GB (BIOS flashed, OC'd and UV'd) getting about 13.5 to 14 MH/s per GPU for ETH
OS: Windows 10 PRO 64 - Latest Updates Installed
AMD Driver: 18.1 (I find this version most stable so far on all of my rigs)
Risers: Versions from 8S to 9S
I did not make any changes in BIOS - everything left on stock settings since I purchased it last week.
I am using every PCIe slot except #5 (for some reason I skipped over this one - don't remember exactly why)
I installed the first 4 GPU's one at a time from PCIe slot #1 to PCIe slot #4 with no problem.
When I got to GPU #5 I had to Shutdown the rig - flip power switch for the PSU to OFF - Install the riser on PCIe #6 - Turn PSU switch back to ON and turned rig back on. I was able to see the 5th GPU with no issue - Applied the AMD clock/time patch - Rebooted and all 5 GPU's are present.
I am currently waiting for another riser and a M.2 adapter to arrive from Amazon so I can try GPU #6. I'm not sure if I will need the M.2 adapter or not I am getting it just in case. I was not planning on going more than 6 GPUs on this board. I keep all my rigs at 6 GPUs. That's the standard I follow. This is my first AMD build. I have 3 Intel Celeron rigs that run for weeks at a time with no problem. I want to try AMD if possible - I am a fan of the Ryzen CPU's. So far the 5 GPU's have been running for almost a week no crashes nothing. When I first turned the board on for initial setup I was using the onboard video and got no video at all - I thought I had a bad board at first - I didn't realize that the video is set to dedicated PCIe slot automatically - I plugged in a riser to PCIe slot #1 and was good to go - Just some info for anyone running into this issue.
I will post my results with GPU #6.
If anyone is interested in any help you can contact me and I will provide you with my services.
Thank you! - Trap
trapcrypt@gmail.com