Show HN: Homemade 32-bit CPU and OS (2015) [video]
This reminds me of http://nand2tetris.org/ (and the accompanying Coursera course). It's a fantastic course to learn about computing from first principles.The course starts off with just a few logic gates and how you can combine these to make more complicated circuits. These are in turn combined to reach higher levels of abstraction, until you finally have a 16bit computer, with 16K of ram. 
It's a really cool course that helped me flesh out my understanding of what's going in my computer.