Stanford's experimental operating systems course[0], where you buy a Raspberry Pi and write your operating system on the bare metal by using the reference specifications.
"You should take this class if: 1. You write code well OR (you don't yet write code well AND have a lot of time to devote to the class); 2. AND you find these systems topics interesting.
The people that found the class valuable in the past were entirely drawn from this demographic. (In particular: I would not take this course if you were looking for an easier way to satisfy a cs140 requirement.) We are trying to go as far as possible as quickly as possible with a group interested in doing so." [emphasis mine]