Late 2020 Mac Mini: Apple Silicon M1, Thunderbolt 4, USB4, PCIe 4.0

One thing to note is that the JHL8040R is a TB retainer not a controller. The difference is a controller “speaks” the TB protocol and exposes USB, PCIe, and DP signals to the (typically) PCH and/or Intel CPU. They’re typically 10-20W and, from personal experience, absolute shit to work with (buggy firmware).

A retimer is a < 1W part that just strengthens the TB signal coming from the outside world and cleans it up so the controller (integrated in the M1 here presumably) does not have to deal with a weak or noisy signal.

Important to note that Intel plans to integrate a TB4 controller in their future (mobile?) processors but seems like Apple beat them to it. Also it’s unclear if M1’s integrated TB controller is TB3 or TB4 (you can have a TB4 retimer drive only TB3 signals).