AMD have recently made building a new system around their processors a little complicated due to the compatibility, and moreso the backwards compatibility, of their processors and the motherboards that use the 3 very similar sockets for current AMD processors. Hopefully this guide will help to make things a little clearer.

SOCKET AM2 - This socket supports all AMD Athlon 64 (including single core and X2 models) and Sempron CPU's. This was the first of the AMD Socket AMx designs. This socket can also support AMD Phenom processors but support is down to individual motherboards. If you have a socket AM2 motherboard and plan to use an AMD Phenom processor on it, you must check the motherboard manufacturer website to see if it is possible. The chances are that if your socket AM2 motherboard does support the Phenom series, it will still need a BIOS update before it can do so. Note also that if you install a Phenom CPU to a socket AM2 motherboard, the Phenom will perform a little slower than normal as this CPU is designed to use features and an HT speed that socket AM2 cannot support.

SOCKET AM2+ - This socket was the first update to the original socket AM2 and support ALL processors that are compatible with socket AM2, along with all AMD Phenom processors and the new Phenom II processors. You can even use the new socket AM3 processors on this socket. It could be said that if you are unsure then buying a Socket AM2+ motherboard is a fairly safe bet for your AMD processor. Unfortunately it is not so clear cut. Some AM2+ motherboards cannot support specific AM2+ Phenom processors, particularly the Phenom X4 9850 and 9950. This affects socket AM2+ motherboards using the AMD 780 series chipset. It is essential that you check your motherboard manufacturer website for CPU support if you are using an AMD 780 series chipset motherboard.

SOCKET AM3 - This is the latest incarnation of the socket AMx design and is also the strictest in terms of what it can support. This socket can only support socket AM3 processors, namely the specific socket AM3 Phenom II's. This socket introduces DDR3 RAM support for AMD Phenom II and the fact that it uses DDR3 is the biggest reason why it can only support socket AM3 processor and offers no backwards compatibility for socket AM2 or AM2+ processors. If you are looking to buy a new AM3 Phenom II processor and want DDR3 in your new system, this is your only option.

Hopefully this guide will make choosing the right processor and motherboard for your new AMD PC easier.