AM3 was launched on February 9, 2009 as the successor to Socket AM2+, alongside the initial grouping of Phenom II processors designed for it.

Socket AM3 breaks compatibility with AM2/AM2+ processors due to a subtle change in key placement.

Tom's Hardware removed the two obstructing key pins from an AM2+ Phenom processor in order to fit it into an AM3 socket.

Despite using an AM3 socket and despite using a northbridge and southbridge found on AM3 motherboards, they support any AM2, AM2+, or AM3 processor.

[6] As AM3 processors also support DDR2, they are backwards-compatible with Socket AM2/AM2+, contingent upon a BIOS update for the motherboard.