Re: Having a stupid moment.
AMD isn't as picky about RAM speeds like Intel is right now. (that is to say, Intel boards do much better with faster RAM than AMD systems do)
However, upgrading from 1066 to 1333 WILL give you a bit of a speed boost on an AMD board, and you're not being mislead, AMD's on die memory controller only officially supports DDR3-1333. Speeds higher than that require overclocking, which is fine if that's what you want to do, but in a stock config, 1333 is the end of the line for AMD.