For those who want to learn how CPUs and computers work, Nand2Tetris is a great book that takes you from logic gates (NAND) to making a CPU that plays tetis
I just finished the course from coursera https://www.coursera.org/course/nand2tetris1. It is a very good start learning from the course or from the book for those who are interested to build something like this. I highly recommend it.
http://www.nand2tetris.org/