Quote from: citronick on November 18, 2016, 12:54:34 AM

8 x GPU under Windows is a lost cause.... but looking at your build, maybe relook at the PSU - suspect its cause of black screen....

I have a 7 x R7-370 built in June for ETH mining working like a charm.

Although the 370 is not really a fast card, its a very stable, super cool card and is not power hungry.

ATM, its mining ZEC at 58-60 H/s per card with Claymore v6 ZEC miner.

I spent so much time tweaking to get the 8th card to work but no good results.

I stopped experimenting after realising that those downtime should have been put to good use mining and getting profits. 7 cards not put in good mining use is really a waste...

Conclusion to share:

1. Beyond 7 GPU, only Linux can make this happen. Some dude in Ethereum forum has shared this in detailed.

2. Crazy multi GPU Linux rig, I think this dude went all the way to 18 (or more) x GPUs to mine ETH using a special USD$2000 PCI extension board usually meant for deep learning systems. Even Claymore had to release a special Linux version to support it for ETH mining.
See: https://bitcointalk.org/index.php?topic=1676763.msg16895926#msg16895926

3. For Windows 7,8.1,10 - max 7 cards with standard drivers is no issue esp with latest drivers. Older drivers, need the 6xGPU hack utility.

4. Windows Advanced Server with special drivers and Windows registry tweaking - 8 or more cards possible. Google "Deep Learning systems" that are Windows based.

I have 8x280x on same rig and everything is fine. I think the problem are new graphics cards (Rx series), with old card (HD 7950 or R9 280X) my rig start normal. 8x 280x works perfectly on same windows 10, and same 16.9.2 driver.