Overclocking Performance & Power Consumption
The Radeon HD 7770 and HD 7750 have aggressive core and memory clocks by default, but there's still plenty of headroom for overclocking. We pushed the former from 1000/1125MHz to 1150/1250MHz and the latter from 800/1125MHz to 950/1250MHz. Both were decent overclocks to be sure, but they only resulted in another 1-3fps in Crossfire.
We usually expect multi-GPU configurations to be at the bottom of our consumption graph as they are notoriously power hungry. While the HD 7770 Crossfire setup is toward bottom, they still use slightly less power than a single GTX 560 Ti. That's even more impressive when you consider the fact that the HD 7770s were 29% faster on average. Similarly, the Crossfired HD 7750s used slightly less power than the GTX 560 while delivering 3% more frames than the GTX 560 Ti.