Totally the wrong forum for this question - Microsoft Home Server!!!
Wikipedia is your friend (please contribute to their current fund raising drive):
AMD confirmed that there is an upgrade path from Socket AM2+ to
AM3:
- AM3 processors work on AM2+ motherboards due to the presence of both the
DDR2 and
DDR3 memory controllers on the processor
- AM2+ processors do not work on AM3 motherboards due to the processor's lack of a DDR3 memory controller
The pin configuration of the AM2+ socket (940 pins)<sup class="reference" id="cite_ref-thdwr_2-0">[2]</sup> is mechanically different from the
AM3 socket (941 pins)<sup class="reference" id="cite_ref-thdwr_2-1">[2]</sup>
Hybrid motherboards
An A790GXH motherboard that can support AM2, AM2+ and AM3 socket CPUs
Some motherboard manufacturers (i.e.
ASRock,
Jetway, and
MSI) have released hybrid motherboards that are equipped with an AM2+ socket and both DDR2 and DDR3 memory slots. These boards permit the use of AM2/AM2+ processors with DDR2 RAM, or AM3 processors with either DDR2 or DDR3 RAM.
Phil P.S. If you find my comment helpful or if it answers your question, please mark it as such.