Neoseeker published a review of AMD's Athlon 64 5000+ X2 Black Edition CPU.

Getting to 3.2GHz with the AMD Athlon 64 X2 5000+ Black Edition was trivial. No need to do anything except change the multiplier to 16 - and presto, you have a X2 6400+! But moving beyond 3.2GHz... now that was a journey. But in the end, it was a succesful journey. The best stable overclock I was able to achieve was a very pleasing 3.396GHz. This was achieved by running the chip at 12x283MHz, and the memory 849MHz.

AMD Athlon 64 5000+ X2 Black Edition Review