X-bit Labs investigates the impact of DDR3 clockspeeds and timings on the performance of AMD's Phenom II X6 processor. The site concludes the results are pretty much as they expected, just as with Intel platforms, the frequency and timings of DDR3 have only a minor effect on the performance of the Socket AM3 platform.
We have not seen anything unexpected in our today’s tests. Like with Intel platforms, the frequency and timings of DDR3 SDRAM may have but a small effect on performance of the Socket AM3 platform. A modern processor has enough cache memory to smooth out any latency that occurs on the path that data takes towards the execution cores. Working in its nominal mode, our Socket AM3 system with a newest Phenom II X6 processor (which has 6 MB of L2 cache) would only get an average 2-3% faster at higher memory settings. The performance may increase up to 5% in some applications that operate with huge amounts of data but this doesn’t change the overall picture. When the system components were not overclocked, there was almost no difference as to what memory was installed: DDR3-1067 or DDR3-1333 or DDR3-1600. You only have to make sure that it works in dual-channel mode.