My 4 GPU RX480 rig has been mining stable with all 12.x versions of Claymore.  When I attempt to add 5th RX480, miner hangs after awhile with OpenCL error.  Miner also doesn't recover, and keep mining; entire system hangs.  My mobo is MSI z170A.  I have modified BIOS to mine with more than 4 GPUs per guides in forums (change pcie to gen 1, enable 4G).

So frustrating trying to figure out how to get 5th miner to run stable.  Have tried with -i 6, -i 5, now trying with -i 7....

Also, not all 5 RX480s mine at 300 H/s.  One is 300 H/s second one real close, but other ones like 250-270 H/s