Ubuntu 7 GPU optiminer zcash rig

Anyone using a Ubuntu 7 GPU optiminer rig?

I have two nearly identical rigs (each):
MSI Z97 Gaming 5 MBO (MBO's are sequential serial numbers)
2 EVGA 1300 Gold PSU
8 GM RAM
7 RX-480 8GB (factory OC)
250GB Samsung 850 EVO SSD

GPU's are mostly Nitro Sapphire but have a few XFX cards.

I used cryptomined work as a starting point (thanks for this work).

Getting Linux to recognize all 7 GUP's was a bit of a challenge but I have a stable (pain in the ass) install process now. I would be happy to share if anyone needs.

I am averaging 210+ S/s on each GPU with this setup.

Problem:
Both rigs show reduced S/s on GPU2 over time. One rig drops output all together and the other drops down to ~50 S/s and stays there. neither GPU2's are off doing something else as their temperature also drops accordingly. Rig that drops to zero on GPU2 (not even listed in log output) hangs, (Ctrl-C) does not bring down miner. Sudo Reboot also then hangs. I need to do a hard reset. Rig at ~50 S/s on GPU2 functions normally for shutdown.

Ive swapped GPU's around, removed GPU's and mined with fewer cards, and mined with only GPU2. results are always the same as above.

Anyone else having this issue?

First thing that comes up is Risers.

that was always a problem with optiminer
dropping gpu, sudden drop of hash rate or hanging all together
that is why i switched to claymore and windows

I just tested Claymore V9.3 on Linux with 7 RX480's and it behaves exactly the same as optiminer on both rigs. GPU2 reduces Sol/s over time and hangs, this is also the 7th PCIe slot on both MB. This points to OS, AMD Driver, or BIOS. I have tried Legacy and UEFI installs and fiddled with the BIOS settings for the PCI bus.

I am leaning toward Linux/BIOS as the issue since its so difficult to install the OS with all 7 GPU's recognized.

I'm running with both GPU2's disabled, since removing them to install in another rig would require a complete reinstall of the OS and reconfiguration on these two rigs.

I have not tried full Ubuntu desktop and have been working with the 16.04 Server version. Should not make a difference but I will try and post the results.

I'd be interested in hearing your install process. I use different boards, but it's always a chore once you get 5+ boards.

I have posted results of Claymore and optiminer on Ubuntu in another topic. I found that Ubuntu Desktop works and server is painful to get working. I still want the server version so will continue to work on this.

One thing I did find was disabling the MBO Ethernet would get the OS / AMD driver to recognize the seventh card. Then once you re-enable it would stay. Used this every time it crashed as it would always drop to 6 cards. was a pain but worked. Had to do this once or twice with Desktop as well.