Indeed, even the official AMD specs are not helpful:
http://products.amd.com/en-us/DesktopCPUDetail.aspx?id=851
These CPUs are guaranteed to work with generic DDR3-1600CL11 (JEDEC spec). With some tweaking it is possible to run quite faster RAM with DDR3-2400CL9 is typically as good as it gets if you are a lucky and skilled AMD overclocker.
You can certainly buy faster RAM and run it slower if needed for compatiblility. I, as well as many others here, can assist you with BIOS settings to get your RAM running at the maximum possible, which varies from CPU to CPU, and RAM kit to RAM kit.