That said GeForce GTX 1080 might receive a substantial boost in memory bandwidth thanks to this cutting edge technology. Leaked picture confirms GP104-400 is using with Micron 6GA77 79TXT modules. Unfortunately those modules are not yet listed in official product catalog, so we are unsure of the exact speed of those chips. However according to WCCF those modules are slightly different in size than normal GDDR5 chips.
An earlier leak of the NVIDIA GP104-200 GPU suggests the GeForce GTX 1070 has 8GB GDDR5 memory clocked at 8000MHz.