I have 1 6 gpu mining rig I recently built and I am concerned as I am not getting the hash power I expected.  I has a msi 1080 in my gamer that I also mine with and get much better rates.  Here is the breakdown:
 
EVGA Geforce GTX 1080 SC x 6
Afterburner set to
+99 Core Clock
+595 Memory Clock
Fan Speed @ 75% (auto leaves it around 68c and this keeps it around 57c)
Power currently at 110% (this is what I am testing now as I have tried moving it around a bit to see if it changes stability or performance/doesn't look to have changed anything going from 90-110)
 
These settings are at best getting 750ish kH/s on each card whereas my msi card is getting around 915kH/s. Mining Gobyte-nepscrypt currently.
 
Any thoughts would be appreciated!
 

I have dual HX1000i Plat (Work Great).  I had thought about the x16 because most of my slots are not x16 slots but didn't expect that much of a decrease.  I'll bump the Power down a bit and next build I'll choose a different MB (for a couple reasons).  I do appreciate your comment!

You can also ask to have this Thread Moved over to the Cryptocurrency Area as well.

Moving thread to cryptocurrency subsection.

bcavnaugh
Difference between a Computer with One Graphics Card over one with Six Graphics Cards.
Your Single Card is most likely running X16 and your Six Cards running X4 maybe one or 2 running X8.
What PSU are you Running?
With this "Power currently at 110%" & "Afterburner set to +99 Core Clock +595 Memory Clock" You are going to Burn up your Cards Mining.

 Bus width is NOT A FACTOR.
 Unlike Folding @ Home, cryptocoin mining does NOT require a lot of work out of the CPU or a lot of bus transfer.
 This is WHY 1x riser based mining rigs work well, when they are a major handicap to cards in Folding @ Home, and why typical 6 GPU Mining rigs get along fine with a dual-core CPU with NO hit to the hashrate.
 The power supply is not going to affect the hashrate, though it CAN affect stability of the rig.
 
 To OP:
 
 If the MSI card involved is the Gaming X, it has a much higher "rated" TDP than the EVGA SC (240 watts IIRC vs 180), which allows it to boost clock higher at the same TDP percentage because the ACTUAL TDP is quite a bit higher.
 68 C is NOT going to "burn up" the card, though there is no real point to the 110% of TDP setting as it's probably not improving hashrate while burning more power vs 90% or so.
 It would help if you would mention *WHICH* MSI card is involved, cards DO vary quite a bit even when it's the same GPU model from the same manufacturer.