DX9 vs. DX10/11

Hey Guys,

I'm new here, just joined yesterday. I have a question, what exactly does "Service Pack 2 Required" mean on the Civ 5 launcher under the DX10/11 option. Is this service pack it's speaking of an OS service pack, or a service pack to the game etc...

Second, does DX10/11 have any advantage to the games framerate, I am satisfied with my current framerate, on medium high graphics, but I've noticed that framerate still dips at times.

Thanks!

---Jason