Hello, I finally built my first gaming PC about a week ago and I heard that the 7970 is a beast with overclocking. I had no idea how to OC, so I read some things and took some notes and started testing. I got to around 1050 MHz and at that point I got glitches and artifacts. I bumped up my VDDC a little (to about 1150) hoping that would work, but it didn't. I reset and I tried again today but the same thing happened. How much voltage do I need to get a stable overclock and boosts my overall performance by about 15%? If that's possible
anyways, thanks 
SPECS:
i7 3770 3.4GHz
Corsair CX750
Sapphire 7970 Dual-X
Kingston 2x4GB DDR3
Western Digital 2TB HDD
SPECS:
i7 3770 3.4GHz
Corsair CX750
Sapphire 7970 Dual-X
Kingston 2x4GB DDR3
Western Digital 2TB HDD