Hello EVGA,
 
I recently purchased a B-Stock GTX 980 SC ACX 2.0 to SLI with my GTX 980 ACX 2.0.
I should have purchased a Non SC version to match them but I bought the card when only SC was available.
Now I received the first SC version and it did not boost to 1367 MHz as advertised and the lighting for letter E for EVGA did not work so I RMA'd and received a new one.
The new one boosted to 1400 MHz out the box and passed stress test and games were perfect on it. Once I activated SLI with my Non SC version, things started going down hill.
Any overclock will freeze up the system so I would have to hard reset.
If I turn off all OC, (both cards will run at 1253 MHz) it passes the test SOMETIMES.
It would freeze and lock up my system or the driver will crash at random times with games like (CS:GO and Dota 2).
I've already did a fresh install of Windows 8.1 and the problem still persists.
Is the problem caused due to the difference in the clock speed?
 
Things that I have tried-
1. Tested the cards individually. Both cards can be overlocked decently and pass all tests and games would run perfectly fine.
2. Tried 2 different SLI bridges. Both freeze the system sometimes.
3. Any OC will immediately crash and lock up the system.
 
My System -
i7 4790k stock, NZXT x61, Asus Maximus VII Hero MB, 16 GB ram, 1 TB Samsung SSD, 1 GTX 980 ACX 2.0 + 1 GTX 980 SC ACX 2.0 & 1000W EVGA P2 PS.
 
I would LOVE to return the card for a Non SC version but all the representatives told me they would have to charge 15% restocking fee.
 
Edit: The first SC version card also crashed and froze the system even though the core clock was around 1320 MHz.

Sajin
Try moving the sli bridge to the other set of sli fingers to see if it helps. Try driver 347.88.

Oh sorry I forgot to mention that I tried that as well. I'll try 347.88 driver once I get home. Thanks for the suggestion.

Zuhl3156
When mixing video boards I always got the best results by boosting the 'vanilla' version to match the superclocked speed. The only way I ever had things stable was with matching identical clock rates.

To boost the "vanilla" version only, I have to turn off the synchronization between two GPUs option in MSI afterburner correct? Then I select the "vanilla" card and boost to match the SC version?

Zuhl3156
Yep, turn off 'sync similar similar graphics processors' and just boost the vanilla board to match the S/C board. After that you can start upping each Core Clock equally for better performance if needed.

What happens if the Vanilla card cannot even reach to the SC default clock speed? From what I remember, my SC version boosts to 1405 MHz or so out the box. My vanilla card boost to 1253 MHz and I remember most stable clock speed I got without adding any voltage was about 135 MHz. So that adds up to about 1388 MHz. I hope that should be close enough to stop the crashes..
I froze so many times during CS:GO MM and Dota 2 which pissed off alot of the players during the session lol.

isdouble
If I turn off all OC, (both cards will run at 1253 MHz) it passes the test SOMETIMES.

They should both be able to do this easily.

Good to hear that increasing the voltage helped. The cards should pass benchmarks at completely stock clocks without having to add any voltage.