well in the above link it says the deneb am3 chips will still work in a am2+ boards but just with ddr2. where putting the chip in a am3 board u can use ddr3.The 1st set of chips will be socket AM2+ which will also work in AM2 sockets. Thereafter it will be socket AM3 only
the deneb am3 chips have the same layout pins as the am2+..
AMD's upcoming Deneb AM3 chips will make it easier for users to upgrade as it won't only work in AM3 sockets, but is also compatible with the AM2+ socket as they use the same pin-layout. When used with AM3 it will use DDR3, with the AM2+it will be using DDR2.
This will allow you to keep your AM2+ motherboard and DDR2 memory when upgrading to the next generation of AMD's CPUs.