TechPowerUp reports leaked slides reveal that AMD's Tonga GPU supports a 384-bit GDDR5 memory bus instead of the previously thought of 256-bit wide one, which is found on the Tonga-based Radeon R9 285 graphics card. This means AMD is likely to launch a faster part with a 50 percent higher memory bandwidth than the R9 285.
This isn't the first time AMD has done something like this. Its "Tahiti LE" chip was essentially a "Tahiti" die placed on a smaller package with pins for just a 256-bit wide memory bus, on the oddball Radeon HD 7870 XT.
What this means is that AMD's next performance-segment graphics card based on the "Tonga" silicon, could feature 50% more memory bandwidth than the R9 285. The stream processor count is still 2,048, but these are more advanced Graphics CoreNext 1.2 stream processors, compared to first-generation ones on "Tahiti," offering more performance per Watt. The TMU count remains 128, although there's no clarity on the ROP count. Estimates are split between 32 and 48. The R9 285 has 32, and so does "Tahiti."