Socket Compatibility

Socket Compatibility explained: AM2+ and AM3

We keep repeating this tidbit in our AMD processor reviews. But we feel it is imperative to explain. AMD has an approach we here at Guru3D like to see very much. That is try to stick as long as they can with a processor socket design. Therefore the good news is, even if you have an AMD 790 AM2+ compatible motherboard, you can pop in a new AM3 processor and it'll work.

Mind you that if you do so, and this is a very strong recommendation, upgrade your BIOS (motherboard BIOS) before upgrading to the new processor, to gain the latest Phenom II compatibility straight out of the box. Motherboards wise any AMD 790 FX or GX chipset purchased last year should be compatible with Socket AM3 processors. Some of you might even have luck with slightly older AMD 780 chipset based motherboards. But for 780 motherboards there is a second restriction, please do make sure your motherboard can handle the power requirements of the processor. Please check this with your motherboard manufacturer.

What is the big deal about Socket AM3 then?

Socket AM3 based motherboards are introduced with merely one thing in mind, to get DDR3 memory support.

Todays reviewed processors are in fact Socket AM3 processors. So (and again to make it clear) it will fit fine on Socket AM2+ motherboards which support Phenom II. The only snag is that you are forced to use DDR2 memory, though the performance hit really is marginal.

What's the physical difference in-between the two sockets?

Two extra pins (940 for AM2+ vs 938 for AM3) makes the older chips mechanically incompatible with the new socket, preventing users from attempting to install an old chip in a new board.
So if you want to go for DDR3, a migration to a Socket AM3 motherboard is mandatory. Once you do have a Socket AM3 motherboard, you'll get support for up-to DDR3 1333 MHz memory. On socket AM2+ you'll be able to make use of DDR2 1066 MHz memory, while on socket AM2 you'll be limited to 800 MHz.