For some odd reason, Evga names that switch slave/master on the back of the backplate. It is actually a Quick Switch Dual BIOS designed to switch between the card's dual BIOSs. I have the 960 FTW also, and it has the same switch: http://static.evga.com/articles/00897/images/features/bios.png
I haven't delved into it too deeply yet. But in one position, the fans only run when the temp exceeds a certain limit.
Unrelated question...
What does Evga Precision (or GPU-Z) show your load clock speed as being?
When I first saw that switch, I thought it was a BIOS switch for EUFI to legacy that allowed the new Maxwell GPU-equipped card to work on older boards. But I haven't found verification of that yet.