Most AM2+ motherboards today also support AM3 processors by simple bios updates. Same is the case with Asus. However, I am not sure about the difference between the previous M3A Series AM2+ boards and their M4A Series (e.g. M4A78-EM / VM) AM2+ which indicates that the boards are "Brand New Design and Optimized for AM3". This is purely qualitative and I can't find further explanations anywhere. Does this mean that those with simple "AM3 Support" AM2+ boards are not as good as those classified as "Optimized for AM3?"
I am planning on using an AM3 Processor on and AM2+ board (to use my DDR2 memory with low latency) and I am a bit curious about the positioning of these new boards from Asus. On top of that, there is a price premium for these boards, and hopefully, this translates to better performance.