Using TECS to go from NAND gates to assembly is 4-6 evenings worth of work and totally worthwhile. I have a rough idea how compilers and operating systems work but until TECS everything below that was run by little laptop pixies.
I think I'm going to have to get this TECS book (no pun intended) - it sounds just what I'm after. Need to finish SICP first though :P Not enough hours in the day.