Quote:
Originally Posted by
Cleeecooo 
How so?
and as we know this cards are cherry picked for reviewers ...
Look for reviews, and compare them with the other ones... You are paying a premium tag and getting no benefit out of it..
For example
MSI Lightning
Regardless of BIOS switch setting, the highest stable overclock we achieved was 1175 MHz on the core and 1800 MHz for the memory at a voltage of 1.25 V.
Gigabyte
We were able to stably overclock our sample to 1200 MHz and 1600 MHz for the core and memory, respectively, using a 1.25 V setting.
HIS
With a voltage setting of 1.25 V, we took our sample to 1250 MHz core and 1800 MHz memory frequencies, achieving the highest stable GPU overclock in this round-up. Our only complaint is that iTurbo doesn’t offer control over AMD's PowerTune technology. So, we had to choose the maximum setting in Overdrive before changing the clocks.
Sapphire OC
We were able to push Sapphire's card to a stable 1175 MHz core and 1800 MHz memory overclock at 1.2 V.
Visiontek (reference)
While this card's core didn't scale quite as high as some others, its memory turned out to have quite a bit of headroom available. We managed a maximum stable core overclock of 1125 MHz, with memory operating at 1900 MHz. That's the highest memory overclock in this story. We went with a 1.2 V setting, too.
Source:
http://www.tomshardware.com/reviews/radeon-hd-7970-overclock-review,3186.html
