We have been hearing about the Tonga GPU for a little while now and it has just recently been revealed that the graphics card based on the new GPU will be called the Radeon R9 285. The Tonga GPU will replace the Tahiti core which has had a lifespan of almost three years now.
If you did not know the Tonga GPU is simply the Tahiti GPU with a shorter memory bus. Tonga is said to have the same number of Streaming Processors as Tahiti. For this reason it is believed that Tonga will completely replace Tahiti-based cards (R9 280, R9 280X) in the coming months.
The report says that the R9 285 will make use of the Tonga PRO GPU so there still is a chance for a Radeon R9 285X with Tonga XT.
The only real major difference between Tahiti and Tonga cards is limited to frame buffer size and interface width. Tonga is likely to launch with 2 GB of GDDR5 memory, but that will not stop AIB partners from released 4 GB cards.
The AMD Radeon R9 285 is expected to launch somewhere between late August and early September.