This topic is something I really wanted to cover last year, but due to work scheduling (hah!), I was never able to fully formulate it into a presentation format. But I felt it had to be covered before Vega's release.
Hopefully the presentation makes sense for you guys, it's not an easy topic to talk about in simple terms.
References:
http://www.anandtech.com/show/11223/quick-look-vulkan-3dmark-api-overhead
http://www.nvidia.com/content/pdf/fermi_white_papers/nvidia_fermi_compute_archi
آی-ویدئو