6GPU Problem Xububtu

[harisz]

Hello, I got a big Problem with my Rig. When I run 5 GPUs, everything is fine - more or less.
But when I add the 6th GPU, the System is not stable anymore.
First Linux starts getting really slow and has problems on booting. Sometimes it gets stuck at the boot-screen and i have to power off/on to start the rig.
Then I start the Claymore miner and I can see that the 6th GPU is running on 19-20Mhs only (should be 26 at least).
After a while things start getting weired. Alle the GPUs begin to slow down on MHs and GPU numer 6 goes down to 4-5MHs. Few minutes later the system freezes and thats it - i have to manually power off.

Here is my Rig:
Intel G4400
Msi Z 270 A Pro
2*Corsair CS650M
4GB Kingston Fury Black
4* RX 470 Sapphire Nitro+
2* RX 480 Sapphire Nitro+
Xubuntu 16.04.2
Driver: amdgpu-pro-17.10-414273
Claymore dual miner 9.5

(I have already tried to use a different 6th GPU, but I get the same errors, so the GpU is fine)

Claymore Pic: http://imgur.com/a/CgxUV

[erk]

Is the 12 volt rail collapsing?

[harisz]

Not really sure about that, how to find it out?

[harisz]

Does anyone know why this happens?
Today it happened again..

I mined with 5 GPUs since yesterday evening - everything fine.
Then i added the 6th GPU.. after 10 Minutes the Hash rate went from stable 158mhs to 155,154,153 and so on.
For about 10 Minutes MHs went down slowly (on this GPU) and then it showed "GPU0 - off".
5 Minutes later the rig freezes and thats it.

[car1999]

maybe it's due to your weak PSU, try to use a stronger one.

[harisz]

I dont think that it is a PSU Problem.
One of the PSUs fires up 2*rx480 1*rx470 and the CPU.. the second PSU (the one with the problematic GPU) got only 3*rx470

[erk]

Not really sure about that, how to find it out?

Use a multimeter and check it.

[harisz]

I have tried another PSU now - still the same problem

[harisz]

Updated BIOS.. nothing changed