As I said, it's a few years ago. Today you can get 5 GHz with Sandy Bridge on air (although it might entail testing a few dozen CPUs to find one that can reach that high).

But the OP was referring to speeds up to 10 GHz, those still need something special. Here's a current Guiness record, 8.4 GHz using liquid helium: http://www.youtube.com/watch?v=UKN4VMOenNM

Other materials might potentially clock higher, an IBM research prototype chip reached 500GHz: http://news.bbc.co.uk/2/hi/technology/5099584.stm