Processor Types and Specifications - Upgrading and Repairing PCs - page 96

Although Socket AM2 contains 940 pins—the same number that Socket 940
uses—Socket AM2 is designed to support the integrated dual-channel DDR2 memory
controllers that were added to the Athlon 64 and Opteron processor families in 2006. Pro-
cessors designed for Sockets 754, 939, and 940 include DDR memory controllers and are
not pin compatible with Socket AM2. Sockets 939, 940, and AM2 support HyperTrans-
port v2.0, which limits most processors to a 1GHz FSB.
Socket AM2+ is an upgrade to Socket AM2 that was released in November 2007. Al-
though Sockets AM2 and AM2+ are physically the same, Socket AM2+ adds support for
split power planes and HyperTransport 3.0, allowing for FSB speeds of up to 2.6GHz.
Socket AM2+ chips are backward compatible with Socket AM2 motherboards, but only
at reduced HyperTransport 2.0 FSB speeds. Socket AM2 processors can technically work
in Socket AM2+ motherboards; however, this also requires BIOS support, which is not
present in all motherboards.
SocketAM3wasintroducedinFebruary2009,primarilytosupportprocessorswithinteg-
ratedDDR3memorycontrollerssuchasthePhenomII.BesidesaddingsupportforDDR3
memory, Socket AM3 has 941 pins in a modified key pin configuration that physically
prevents Socket AM2 or AM2+ processors from being inserted (see Figure 3.17 ).
Figure 3.17 Socket AM3. The arrow (triangle) at the lower left indicates pin 1.