Was at the apple store last week and an older Apple rep came to assist me while i was testing out the 13" rmbp attached to the thunderbolt display. He started to explain how the Thunderbolt display has its own gpu that kicks in if its stonger than the computer powering its gpu... I was jaw dropped and very impressed but still skeptic as I had never heard such a thing and consider myself pretty knowlegeable on current tech. He then started telling me about the 13"s Iris "Pro" graphics which quickly put him in the crazy old man category and i was immediately able to write off everything he had said prior. Until I stumbled on this http://www.maclife.com/article/howtos/12_possible_uses_thunderbolt_port Number 5 Does the TBD have some kind of GPU? I brief Google search turned up blank.