de acordo com o forum oficial da gigabyte, tirando os bulldozers, os outros processadores da amd só suportam 1333mhz e usar mais que isso força a controladora da memória do processador. com isso, vale mais a pena "apertar" os timings da memoria que aumentar o clock.
segue:
You are better off not trying to run your RAM above 1333 Mhz. when using an AM3 Phenom or Athlon CPU.
If you do so, you run the risk of system instability and even damaging the Memory Controller on the CPU. If, like me, you have invested in 1600 Mhz RAM, you will actually benefit from running your RAM at 1333 Mhz and tightening the timings. You also gain better performance by slightly overclocking your CPU. If, however, you do overclock your CPU, it is stongly recommended that you purchase a good quality 3rd party CPU heatsink to aid CPU cooling and also remember that officially, neither Gigabyte or AMD support overclocking of their products.