Working at the layer below is a very useful exercise. As part of my undergrad course in EE in the late 1980's we had to design and simulate a 4 bit micro-processor using logic components (essentially NAND gates). I got completely immersed in that project. Not only did it force me to understand a complete, albeit simple processor but actually building it gave me a lot more confidence in writing code. Things have moved on a lot since then and there are many layers of abstraction meaning that most developers don't need to understand the hardware, but having a decent 'programmers model' for the OS can only be a good thing.
I built a 4 bit microcontroller the same way around 2000. We flashed the gates to an Altera EPROM and other than external memory chips, the state machine, ALU, and other sub systems were assembled using logic gates we burned. We supported 16 instructions and could access 16 words of memory. That was enough to code a "password" based security system that would either grant access by raising an external line or it would output an alarm state if the code was invalid. As I recall it could only handle about 25Hz max. Still one of the most influential projects I worked on in college.
