I was self-taught in high school on computer architecture by reading book. I didn't own a computer, understand, but these book served the same purpose in terms of learning CPU architectures and machine language programming. The 6502 was the CPU I studied.

In 1985 as an EE student, I took a course in modern CPU architectures. I still recall having my mind blown when learning about branch prediction and speculative execution. It was a humbling moment - as was pretty much all of my studies as CMU.