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Georgia O'Keeffe's Canyon with CrowsThis was originally painted in the Palo Duro Canyon in Texas, which is around the area I originate. Oftentimes I feel homesick just thinking about it, even though I've not visited Texas in over thirteen years. Even though this particular painting is fairly abstract, it catches the magnificence of that place really well: The clarity of the sky, the rolling landscape, the sparse vegetation, the beautiful red rocks... and of course, the crows. The idea that the cycle of life and death continues, even in such a desolate place.It makes me homesick.

Back up a tick.Suppose we have an instruction whose opcode field contains 101 010, and that means ADD.The only requirement this places on the machine is that when it commits the results of this instruction, that the final change in the machine state is consistent with doing the requested ADD.You’ll notice I added a ton of abstraction and weasel wording in there. That’s because, in a modern, mainstream CPU, the opcode encoding is fairly abstracted from what the processor actually does.In a simpler processor, they’re tied more closely together.Now here is where I cheat a little, because I know the OP has had an architecture class where such a simpler processor came up.In particular, in the context of that simple processor, the ALU control lines are driven by an instruction decode ROM. And, a table like this one determines what that ROM outputs.So, in a simple CPU, the signals involved with doing an ADD need to, at a minimum:Make sure the adder sees the correct argumentsMake sure the output of the adder get committedThat’s it. If there are other pieces of hardware that compute AND, OR, XOR, SUB, shift, etc… and the hardware ignores the result, then “so what?” It is a power concern, but it’s not a correctness concern.I really suggest you go back and review that architecture course that went through the “brain dead processor.” That’s the right material to review right now.

Become a TA. When you have to teach someone else who is struggling with basic concepts and also having trouble understanding your attempts to explain it to them, that's when you will really start to understand things on a very fundamental level. In figuring out their misconceptions, and then in figuring out how to explain it so they can understand it, you will find that you will understand it far better yourself. At that point, it becomes intuitive.When you learn something that's fairly abstract, try to relate it to something concrete. Try to create simple (often extreme) examples to help you understand whatever it is that the equation or whatever is trying to convey. Try to understand what each term in an equation is trying to convey - what it means on a fundamental level.