During the R9 285 launch yesterday in India, PC Watch had the chance to get some information about the full Tonga architecture in an interview with Raja Koduri (They didn’t say if it is straight form Raja Koduri or not). But they are sure about that the tonga will have 384-bit bus because due to the Full tonga having six memory control each 64 bit wide. It seems that full tonga and Tahiti share the same configuration because there will be 32 compute units with 2048 stream cores in total.
AMD Tonga with Heterogeneous System Architecture
Tonga would be in the final fourth state of HSA implementation while Kaveri is still in its third stage. Another report made by PC Watch is that Tonga is HSA-Compatible. Which clearly means that the GPU Compute Context Switch and GPU Graphics Preemption is already present in Tonga.
The first ever graphics card with Tonga GPU was R9 285. There will be 2048 unified shaders packed in the full chip known as XT compared to Tonga PRO which has only 1792 stream cores. Although still a rumor PC Watch also claims that there are more than 32 ROPs in Tonga XT. Maybe the configuration of 48 ROPs was the main reason behind why the R9 285X was held back till Geforce 900 announcement. With the 284-bit interface, It could be a tough competitor for the GTX 970.
But there is less chance it will be released next month and if it don’t then it might launch under 300 series later this year.