The memory controller might have been upgraded in the c3 revision phenomII . The memory controller officially supports
As you can see, not much has changed, but it does seem to be for the better. I want to put emphasis on the fact that it now supports four DIMMs at 1333MHz officially instead of two, so it looks like the memory controller has been upgraded. http://www.neoseeker.com/Articles/Hardware/Reviews/pii_2ndcorerev/
Anything above that is going to be on a user basis, because its overclocking beyond 'official' specifications.