I cannot get more than 4 cards to initialize when mining Grin at the same time. On my 6, 7, and 8 card rigs anything over 4 cards throws initialization errors in the beginning.

  password:         x
Power calculator:   on
Color output:       on
Watchdog:           on
API:                off
Log to file:        off
Selected devices:   GPU0 GPU1 GPU2 GPU3 GPU4 GPU5 GPU6
Temperature limits: 90C  90C  90C  90C  90C  90C  90C
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22:18:26 Failed to initialize miner on GPU4: GIGABYTE GeForce GTX 1070 8GB:
22:18:27 Failed to initialize miner on GPU5: GIGABYTE GeForce GTX 1070 8GB:
22:18:28 Failed to initialize miner on GPU6: GIGABYTE GeForce GTX 1070 8GB:
22:18:28 Connected to grincuckaroo29.usa.nicehash.com:3371
22:18:28 Authorized on Stratum Server
22:18:28 New Job: 1777603967957 Difficulty: 1
22:18:28 Started Mining on GPU0: GIGABYTE GeForce GTX 1070 8GB
22:18:28 Started Mining on GPU1: GIGABYTE GeForce GTX 1070 8GB
22:18:28 Started Mining on GPU2: GIGABYTE GeForce GTX 1070 8GB
22:18:28 Started Mining on GPU3: GIGABYTE GeForce GTX 1070 8GB
22:18:31 GPU3 Share Accepted 120 ms