The Radeon HD 7970 has a reference clock of 925 MHz, but most of the cards are easily overclockable to at least 1100 MHz. It’s already known that a clock of 1050 MHz makes this card already faster than GeForce GTX 680 2GB, and that’s the whole point of this new version.
AtomicPC asked AMD, why did they wait with GHz Edition in the first place. They claimed that actual yields are now better and require lower voltage to sustain 925 MHz core clock. The newest chips can be overclocked up to 1250 MHz, so this can bring the crown of performance back to AMD for at least some time.
The actual overclocking (not performance) ranking would look like this (roughly estimated by hwbot and multiple reviews):
- AMD Radeon HD 7970 6GB (up to 1300 MHz Sapphire Toxic 6GB)
- AMD Radeon HD 7970 3GB GHz Edition (around 1250 MHz)
- AMD Radeon HD 7970 3GB (around 1200 MHz)
- NVIDIA GeForce GTX 680 2GB (around 1180 MHz)
- NVIDIA GeForce GTX 680 4GB (around 1150 MHz)
- READ MORE (Source): AMD gives the 7970 a boost – Graphics Cards – Build – News – Atomic MPC