In early autumn, AMD officially introduced GPU Tonga Pro, which formed the base of video cards Radeon R9 285. A more powerful version of the decision to affix XT was supposed to go out later, but various sources indicate that the corresponding AMD plans were suspended.
In the new Apple iMac computer with 5K-screen you can choose from available two graphics adapters, namely: Radeon R9 M290X with 2 GB of memory on the based on CPU Pitcairn, and the Radeon R9 M295X with 4GB of memory, which is not even mentioned in the official Online AMD. As explained by the site Planet 3D Now, video card Radeon R9 M295X uses GPU Tonga XT with 2048 stream processors and 256-bit interface. Performance computing solutions reaches 3.5 teraflops at a frequency of 855 MHz.
Thus, the graphics processors Tonga XT are available exclusively for Apple.