efficient-portfolio

The CML contains ONLY efficient portfolios (and plots return against volatility; aka, total risk) while the SML plots any portfolio (and plots return against beta; aka, systematic risks) including inefficient portfolios. The XLS David used in the video is located here https://trtl.bz/2Fru70r

I´m not sure if my idea is correct: I understand that an efficient portfolio always is a well-diversificated portfolio but a well-diversificated portfolio could be an efficient portfolio or not. I think that because one of the assumptions for the SML it´s that the portfolios are...