I doubt any one person has full knowledge of how a computer works. I have a reasonably good grasp of most of the software layers, and a fairly good idea of how the hardware abstraction works, but reading about the pentium division bug makes it clear that an undergraduate math degree is not enough to understand the inner workings of the CPU. I understand the performance difference between wifi B and N, but I don't know the protocol details. SSD drives are magic to me. I would guess that full knowledge of how a computer works would require advanced degrees in CS, a couple different maths, and electrical engineering, at the very least.