The clock speed of AMD Barcelona was.....
 

The CPUs were HE or 65W parts said to be running at the same clock speeds. Now 65W isn't a big trick with the Rev F Opterons, but 65W is a trick with a quad core Barcelona. Intel has a massively downclocked 50W Clovertown as well, so it can be done, but this is not a trivial thing.

http://www.theinquirer.net/default.aspx?article=39842