Its not 6.4ghz, that is 3.2ghz.
Im sorry to disappoint you

.
AMD Calclates in there own size shit but if you want to see what it is in GHZ check on google.
6400+ = 3.2ghz.
So still good pc you are getting.
Remeber if you overclock there is a 40% chance of it might break.
Regards
Haldir