It could be the Cool'n'Quiet changing clock speed depending on load change. AMD cpus aren't as smooth with clock change from idle <-> load , so try to see if you see drop in performance when the more performance is needed. That would be a sign of a real issue.
First, check the BIOS for the Cool'n'quite options that you may be able to change around (set to default, if not sure). Try to set the Power Options to "High Performance" and run prime95 to see if you see any drop in performance. The clock should be always running high with this setting. After that, set it to "Balanced" - check advanced setting to see min processor state (default 5%), max processor state (default 100%). With this setting prime should be hitting 100% nearly the entire time the program is running.