07-11-2016, 08:37 PM
I think I would also like to question your hardware. What PSU do you have? The rigs I build with 8 x GPUs in them have 3 x 1600W 80Plus Platinum PSUs. Are you sure all of your GPUs are getting enough power? Ive personally built a good number of systems with 8x290x and never had a problem with ubuntu detecting less than the correct number of GPUs unless there was a problem with a GPU itself or a problem with the pcie slot. All the servers I built have all been ubuntu 14.04 + newest fglrx driver.