There was talk that FP16 (64-bit floating point rendering) could run twice the speed of FP32 (128-bit floating point rendering), is that the case?

Yes it is. Because we have native support in our hardware for FP16 and FP32. So, every pipeline is wide enough to accommodate the full 128-bit through the entire thing -- in the Vertex Shader, in the Pixel Shader and out to the frame buffer. Because we support 128-bit throughout the entire pipeline we added some extra control line and we can split those 128-bit channels into 64-bit channels. Now, that's only in the shading architecture, so we don't get twice as many pixels, but you get twice as many 64-bit in instructions. Also, if you want to use FP16 you'll have a smaller frame buffer so it has a lower footprint in memory as well.