I know that the AM3 CPU have both DDR2 and DDR3 memory controllers on the chip. I thought this would mean that I could buy an AM3 MB and AM3 CPU and use cheap DDR2 for now and upgrade to DDR3 2 years down the line. I am starting to get the impression though that AM3 MB can only use DDR3 memory. Can anyone give me a clear answer on whether or not AM3 Mother boards can support both DDR2 and DDR3?
The CPU can support both, but the motherboard manufacturer determines which. If they choose to support both (very few will), they will provide special slots for each type - and only one type at a time can be used.