Actual return on investment various pre payment strategies

[Kenneth LaVoie]

I know conventional wisdom says "if you pre pay a mortgage, your ROI is whatever the interest rate on the mortgage is". but I KNOW there was an article here that I've since lost track of that showed it's NOT the case. For some reason, you can capture a GREATER ROI than the stated interest rate depending on how early your pre payments are and how much. He laid it all out, and like I said, I THINK it was an article on this very website. Does this sound familiar to anyone?