When the rMBP came out I saw an nVidia 650m on the specs and thought. Its not bad and faster than the AMD6770 it replaces. BUT I only just looked this up. Hang on a second the Nvidia 650m is a 45w TDP chip. Apple have never put in a chip that hot before. For with a 45w heat budget they could have put in an AMD 7870m which is a much faster chip. Why did they choose nVidia ?