***Update***

New info that's probably true

AMD claimed the R9 290X would have a bandwidth >300GB/s. Turns out to be rated at 320GB/s.

AMD claimed the R9 290X would compute at a rate >5 TFLOPS.
Base clock appears to be 800MHz which means 4.5056 TFLOPS
Boost clock appears to be 1000MHz which means 5.632 TFLOPS

Quite impressive. Oh and it has a 512-bit bus.