Putting HDMI ethernet channel thoughts here, since I have no first-hand experience with it. My understanding is that it's basically 100base-TX under the covers,

Putting HDMI ethernet channel thoughts here, since I have no first-hand experience with it. My understanding is that it's basically 100base-TX under the covers, and that's vaguely confirmed by [1] and others. The big difference, as you mentioned, is that it uses a single pair, instead of separate RX/TX pairs like 100base-TX usually does. Rather than doing the 1000base-T trick (share the lines with echo cancellation), it looks like it uses an analog hybrid [2]. Still never seen it in the wild though. [1] https://www.semiconn.com/ep91h1 https://www.semiconn.com/ep91h1 [2] https://en.wikipedia.org/wiki/Telephone_hybrid https://en.wikipedia.org/wiki/Telephone_hybrid