Interesting, yet a bit insignificant news I guess. AMDs Tonga GPUs actually has a 384-bit memory bus, but only a 256-bit interface was used. It is interesting as earlier rumors indeed have been correct in assuming the 280x and 380X would get a 384-bit memory bus.

The guys from PC Per heard that from Raja Koduri (head of the Radeon technology group). Tonga has a 384-bit memory bus, however AMD had a hard time positioning the product in terms the right price / perf hence they tied the products based on Tonga to a 256-bit memory bus. The dillema was simple enough, Tonga with a 384-bit memory bus equal to using more and thus more expensive 3GB and 6GB GDDR5 parts.

So does this mean an upcoming Tonga GPU could offer this wider memory bus? Tonga itself was a follow-up to Tahiti (R9 280/280X), which did have a 384-bit bus, but all along the choice had been made to keep the updated core at 256-bit.  Now more than a year after the launch of Tonga a new part featuring a fully enabled memory bus doesn't seem realistic, but it's still interesting to know that significantly more memory bandwidth is locked away from owners of these cards.

Will we ever see a Tonga/Antigua based product with 3GB or 6 GB with that wider bus, well it's possible alright.

AMD Tonga actually a 384-bit memory bus (but is configured at 256-bit)