Reliable online resources for learning about computer architecture include course websites with lecture notes and homework, which provide a structured approach to the basics. However, lecture slides alone may lack essential details. Hennessy and Patterson's books are highly recommended for in-depth understanding, particularly "Computer Organization and Design: The Hardware/Software Interface, Third Edition" for foundational concepts, and "Computer Architecture, Fourth Edition: A Quantitative Approach" for broader insights into the field. Google Books may offer previews of these texts for initial exploration.