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AMD Sockets: AM2/AM2+/AM3/AM3 And F/FM1/FM2

Upgrading And Repairing PCs 21st Edition: Processor Features
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Socket AM2/AM2+/AM3/AM3+

In May 2006, AMD introduced processors that use a new socket, called Socket AM2 (see figure below). AM2 was the first replacement for the confusing array of Socket 754, Socket 939, and Socket 940 form factors for the Athlon 64, Athlon 64 FX, and Athlon 64 X2 processors.

Socket AM2/AM2+: The arrow (triangle) at the lower left indicates pin 1.Socket AM2/AM2+: The arrow (triangle) at the lower left indicates pin 1.

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. Processors 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 HyperTransport v2.0, which limits most processors to a 1 GHz FSB.

Socket AM2+ is an upgrade to Socket AM2 that was released in November 2007. Although 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 2.6 GHz. 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.

Socket AM3 was introduced in February 2009, primarily to support processors with integrated DDR3 memory controllers such as the Phenom II. Besides adding support for DDR3 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 below).

Socket AM3: The arrow (triangle) at the lower left indicates pin 1.Socket AM3: The arrow (triangle) at the lower left indicates pin 1.

Socket AM3+ is a modified version of AM3 designed for the new “Bulldozer” processors. It has 938 pins, and also supports processors made for AM3 sockets. The table below shows the essential differences between Socket AM2, AM2+, AM3, and AM3+:

Socket
Pins
Supported Memory
AM2
940
DDR2 (dual-channel)
AM2+
940
DDR2 (dual-channel)
AM3
938
DDR3 (dual-channel)
AM3+
938
DDR3 (dual-cahnnel)

Here is a summary of the compatibility between AM2, AM2+, AM3, and AM3+ processors and motherboards:

  • You cannot install Socket AM2 or AM2+ processors in Socket AM3 motherboards.
  • You can install Socket AM2 processors in Socket AM2+ motherboards.
  • You can install Socket AM3 or AM2+ processors in Socket AM2 motherboards; however, the BIOS must support the processor, the FSB will run at lower HT 2.0 speeds, and only DDR2 memory is supported.
  • You can install Socket AM3 processors in Socket AM2+ motherboards, but the BIOS must support the processor, and only DDR2 memory is supported.
  • You can install Socket AM3 processors in Socket AM3+ motherboards, but the BIOS must support the processor.

Although you can physically install newer processors in motherboards with older sockets, and they should theoretically work with reductions in bus speeds and memory support, this also requires BIOS support in the specific motherboard, which may be lacking. In general, you are best off matching the processor to a motherboard with the same type of socket.

Socket F (1207FX)

Socket F (also called 1207FX) was introduced by AMD in August 2006 for its Opteron line of server processors. Socket F is AMD’s first land grid array (LGA) socket, similar to Intel’s Socket LGA 775. It features 1207 pins in a 35-by-35 grid, with the pins in the socket instead of on the processor. Socket F normally appears on motherboards in pairs because it is designed to run dual physical processors on a single motherboard. Socket F was utilized by AMD for its Quad FX processors, which are dual-core processors sold in matched pairs, operating as a dual socket dual-core system. Future versions may support quad-core processors, for a total of eight cores in the system. Due to the high expense of running dual physical processors, only a limited number of nonserver motherboards are available with Socket F.

Socket FM1

Socket FM1 was introduced by AMD in July 2011 for use by accelerated processing units (APUs – CPU plus GPU) and CPUs based on the Llano core. These include the Ax-3xxx series APUs and some Athlon II CPUs, as well as the E2-3200 APU. FM1 has 905 pins in a 31-by-31 grid and uses a PGA socket similar to those used by previous AMD processors. Socket FM1 supports DDR3 memory. It was replaced by Socket FM2.

Socket FM2

Socket FM1 was introduced by AMD in September 2012 for use by its Trinity series of APUs. These include the Ax-5xxx series APUs. FM2 has 904 pins in a 31×31 grid and uses a PGA socket similar to those used by previous AMD processors. Socket FM2 supports DDR3 memory. The figure below illustrates Socket FM2:

Socket FM2 before installing a processor.Socket FM2 before installing a processor.

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