Google's your friend.
Black Edition have unlocked multiplier and voltage. Some say the silicon's better too.
There are lots of way to OC. My version is to increase HTT until RAM's limit then the CPU's multi.
Of course you have watch out for the CPU-NB and HT speed. Put their multi a step down just to be safe. Usually they're safe at <2.2GHz on our climate + cheap air cooling.
I suggest you read about AMD/Intel's CPU architecture first before asking more. You learn more by understanding than asking.