I found myself, using more than 6 Nvidia cards on rig, with or without OC, trying virtual memory between 20 and 90GB (now I keep at 85000MB and works perfect), the rig fails random, one or other GPU is giving error and lock miner and rig too. I used 8xGTX1070 on that rig with Biostar B250 BTC+ motherboard (7xPCI-E 1X and 1xPCI-E 16X), last bios update, 1 stick of 4GB ram, Pentium G4400 GPU (more than needed).

On that times (couple months ago) I found the sollution to "split" rig into more miners (multiple folders with .bat file) so no more than 4-5 cards on miner sequence (.bat file).

Since then, I got no more problems, but I sold all GTX1070 at very good price and replaced with Radeon VII and Radeon 5700XT, doing the same "splitting" cards into multiple miners, because rig with more than 6 cards gives random crashing GPU (same early problem), and lock the miner and the rig too (no self restart).


What I found in time:

Best match power consumption/hashrate for Radeon VII cards is driver 19.7.4 and PhoenixMiner 14.7C, I highly recommend that combination for Radeon VII owners.

Also Radeon VII works great with 19.2.3 drivers and Phoenix Miner 4.8C, even if miner cannot recognize drivers (Unknown open CL Drivers).

Trying with other combinations drivers/miner versions, Radeon VII cannot sustain maximum boost freq for GPU (I use +5% power limit, 1900MHz for GPU and 1100MHz for HBM 2 memory at all cards), and even card is under 65 celcius degrees, GPU boost not increase above 1815MHz ocasionally, most time staying between 173x MHZ and 176x MHz.

Using combinations of driver 19.7.4 and PhoenixMiner 14.7C or 19.2.3 drivers and Phoenix Miner 4.8C (even if miner 14.8C cannot recognize drivers), GPU boost is most time above 186xMHz, making above 97.xxMH/sec with same settings  (+5% power limit, 1900MHz for GPU and 1100MHz for HBM 2 memory at all cards).

Check this printscreen to better understand it (click once more on image, for his largest size).






https://postimg.cc/XBnQ796V