According to the naming scheme of current AMD 6XXX series of lineups, the next flagship card will be Radeon HD7990, called after the current Radeon HD 6990. THe Redeon HD 6990 was a resounding success based on the 40nm process, but the next generation of graphics cards based on a 28nm process will offer even more computing power. AMD misses the 32nm process and is therefore still on 40nm on the Radeom HD 6XXX. This series of graphics chips has so far been successful.
Turning to the technical data specifications that is made possible with the new manufacturing process, the HD7990 is said to deliver performance of up to 12.16 TFLOPS in single-precision calculations and 3.04 TFLOPS in double-precision.Compared to the Radeon HD6990, this means that there is an increase of approximately 58% in terms of performance. 6400 stream processors on the HD7990 has made this possible providing brutal computing potential. It will have 3200 stream processors on a single chip which is almost twice as much on the current Radeon HD 6970. 256 texture units are on board and thanks to the 384bit wide memory interface combined with 6GB of GDDR5 RAM, the card comes with a memory bandwidth of a never head before 576GB/s. For instance, this is definitely possible on a PCIe 3.0 slots which will be featured on the X79 Intel chipset later in the fourth quarter this year.
Interestingly, when it comes to electrical consumption, the HD 7990 humbly only consumes a maximum of 300W and would thus only require a 6pin and a 8pin connector. In idle, it is reported that the card only consumes 30W. Compared to current HD6990 which uses a whooping 450W and GTX590 which is beyond 300W, the HD7990 is a breakthrough in terms of electrical consumption and definitely, the lesser variants in the HD7XXX series will boasts even lower power consuption but yet performing better than current GPUs.
The HD7990 reference card will be designed similarly with 2 slots, in order to dissipate a large amount of heat. DirectX 11, OpenGL 4.2 and OpenCL 1.1 support is expected. The rest of the specifications much remains the same. AMD Eyefinity technology will still be very popular, and AMD HD3D will become more mainstream as more people adopts 3D gaming as the main stay. Of course, the card can still be Crossfired to give you even more computing power in a single computer.
This rumour should be treated with caution as the market can always change. AMD does not want make nVidia out of sight and I definitely think things will change in a year or so when the release date gets nearer. However, it is gratifying to see where development should go and efficiencies goes up.
The following table lists all technical details of rumoured HD7990 compared to HD6990.
Source: http://news.ati-forum.de/index.php/news/34-amdati-grafikkarten/1815-technische-daten-der-amd-radeon-hd-7990-bekannt