Earlier this year, Club 3D had introduced the Radeon HD 7770 GHz Edition with a blistering reference engine clock speed of 1GHz. Now in order to keep up with the heritage, they are releasing the Radeon HD 7970 GHz Edition, which raises the GPU core clock speed from 925MHz to 1000MHz+.
Featuring an extension to the AMD Powertune technology called "Boost", the GPU is capable of dynamically adjusting both voltage and clock speed above the reference clock of 1GHz+. The HD 7970 GHz Edition is the fastest single-GPU graphics card to date, even with extreme settings as well as a resolution of 2560 x 1600.
Source: Club 3D