Sometimes things don't go according to plan. Both AMD and Nvidia were supposed to have shifted to 20-nanometer parts by now. In theory, that's supposed to get you lower temperatures, higher clock speeds and quieter operation. Due to circumstances largely out of its control, Nvidia has had to go ahead with a 28nm high-end Maxwell part instead, dubbed GM204. This is not a direct successor to the GTX 780, which has more transistors, texture mapping units, and things like that.