問題
Q1
I see a port upon the rear USB connector of M7TDA, what is the port for? Why I don't see it on the other model?

That is the LAN function which is inculded under Intel South Bridge (ICH2) Chipset. With Real-Tek LAN chip on board, you don't have to add a PCI LAN card and you can use the intro-net function with M7TDA.