
The reason why AMD designed a new socket for these Opteron processors is to prevent people from using DDR compatible processors in the new DDR2 compatible socket and vice verse.
The extra amount of pins on this socket may be used for integrating a PCI Express controller on the processors.
One of the extraordinary things of Socket F is a clear separation in the middle, probably because both cores have their own group of pins. You can check out the photos over here.