My college (University of Arizona) had a great course in the 80s. It was a two-semester course.

The first semester was digital logic and small-scale integration. You have lectures and laboratory.

• Learn what a NAND gate does.
• Build AND, OR, NOR, NOT, XOR using only NAND.
• Learn about Karnaugh maps, and logic minimization.
• Build a flip-flop.
• Learn about clock signals.
• See how a small addressable memory circuit works.
• See how multiplexing enables larger address spaces.
• See how to make single-bit and multi-bit adders.
• Learn about Binary-Coded Decimal numbers.
• Learn about data registers, accumulators, stacks.
• Learn about instruction pointer registers.
• Make a state machine using a rudimentary combinatorial logic language.
• Explore the 6502 microprocessor, implemented as only 256 lines in the same logic language.

The second semester basically did the same trick as those cooking shows: "Okay, you learned everything you need to know, except how to cook the silicon. Assume it's been in the oven for 20 minutes at 450 degrees. Here's a computer using a 6502 microprocessor."

The whole second semester was learning how to use A, X and Y registers, a stack, page zero addressing, and all of the other opcodes.

What really blew my mind was the synergy: if I wanted to know what an opcode really did, I just read the corresponding line of the "source code" that implemented the microprocessor! We learned the chip-design language, and we could see that each line was just an opcode. Some opcodes took more than one clock to execute, but that was okay, because they took more than one line of source code.

(This also explained to me how someone figured out and published the "missing opcodes" of the 6502. They were just doing the last clock's worth of work for a larger opcode. Sort of like adding a goto label in the middle of a line of a program, then using it.)

I saw today that there's a resurgence of people building Apple I computers (6502, anybody?) just for the sheer enjoyment and education of knowing every circuit in a whole computer intimately. That was one of the last processors that anyone sufficiently interested could really learn and understand inside and out.