Computer Organization and Design ARM Edition: The Hardware Software Interface (The Morgan Kaufmann Series in Computer Architecture and Design)

I agree with jrowley, and here are some resources I can recommend. These are college textbooks, not websites.

First, some EE. Horowitz & Hill's "The Art of Electronics" is the gold standard.

https://www.amazon.com/Computer-Organization-Design-ARM-Arch...

...or Tannenbaum's "Stuctured Computer Organization"

https://www.amazon.com/Structured-Computer-Organization-Andr...