When I was a kid I "wrote" (mostly copied from a programming magazine) a 4-bit CPU emulator on my TI-99/4a. Simple as it was, it was the light bulb coming on for me about how CPUs actually worked. I could then understand the assembly language books that had been impenetrable to me before. In college when I first started using "C", pointers made intuitive sense. It's a very valuable exercise.