If you want for sure compatibility, then go to www.amd.com and look for the suggested mobos they have for their sempron chips, you can even choose by manufacture, and proc model ex. your 3100, or any other amd proc
That would be a s754 board. <A HREF="http://www.newegg.com/app/ViewProductDesc.asp?description=13-131-512&depa=0" target="_new">http://www.newegg.com/app/ViewProductDesc.asp?description=13-131-512&depa=0</A> is nice.