We normally use the Sapphire TriXX overclocking software for our reviews, but this launch was slightly rushed and Sapphire didn't have a version ready to support the HD7770 when we started these tests. We therefore reverted to AMD's Catalyst Control Center.
We pushed the core to 1110mhz, from 1000mhz. Any higher and we would experience instability and hard locking. The memory could be pushed by another 100mhz, to 1225mhz (4,900mhz effective). This translates to an 11% increase on the core, and around 9% on the memory. Decent results considering it is a reference AMD cooling solution.
The modest overclock increases 3DMark 11 scores from 3,498 points to 3,783 points. Not a huge increase, but a noticeable improvement.
Crossfire results are quite good as author said compared gainst more expensive 7950. much like the 5770 I owned, I had two and it was really good.