I don't really do courses anymore, but one thing that kind of matches the questions was playing through Turing Complete.

It's a game where you start with NAND gates, and slowly build up from there. Other gates, then a counter, adder, single-bit memory, etc, where every puzzle uses the component design's you've build before. Eventually you build up to an ALU, RAM, add instructions and connect it up to a working CPU.

It's super fun, and even though hardware isn't really something I usually look into, it has taught me a lot, way more than college courses about CPU architecture. Plus, seeing (and actually programming, in later levels) on a CPU of your own design, using your own opcodes, is actually pretty cool.