Quoting entr0py
and wouldn't that be visible? not only in performance, but in CPU-Z or any of those sorts of programs? and it it's to prevent overheating the time when it would do that would be at load when it's actually hot, not idling.
No the Freq doesn't actually change, only a % of the cycles do anything while idling. You can say it's better at saving power than the Athlon.