Its as if AMD is trying to bridge the gap the GTX 680 has over its Radeon HD 7970. According to this Xbit article AMD is looking to replace the currecnt Tahiti with a 'Tahiti XT2' chip that is clocked at 1.1GHz for the GPU up from the previous 925MHz clock. The power output will be lower via a drop in core voltage to 1.020v drop from 1.175v. Will it work? We will see.
Advanced Micro Devices has been rumored to prepare an improved version of its Radeon HD 7970 graphics card in order to better compete against Nvidia Corp.'s GeForce GTX 680. What has not been known so far is that the new version of AMD's top-of-the-range single-chip graphics solution will also feature a new chip revision with higher frequency amid lower voltage.
Known under Tahiti XT2 code-name, the new flagship graphics processor from AMD will get 1.10GHz (1100MHz) clock speed, a 18% increase from the default 925MHz; as well as lowered core voltage of 1.020V, a 14% decrease from 1.175V implemented on the Radeon HD 7970 graphics card. Thanks to lowered power consumption and increased clock-speeds, AMD will probably use the code-named Tahiti XT2 chip for its flagship dual-chip Radeon HD 7990 solution, reports Ocaholic web-site."
Source: X-bit Labs