Had a phone interview with many small questions related to computer architecture, operating systems, and programming. I was then offered an onsite interview.

My onsite interview was with 5 different people. Each interviewer seemed to cover different topics. Again, questions came from computer architecture (I/O, memory hierarchy, etc.), operating systems (cache consistency, virtual memory, etc.), and programming (C, C++, assembly). The last interviewer asked more general questions, such as "What would you do if you were in this situation?" and "What do you think about the future of computers?"

It wasn't about being difficult, but they kind of tried to focus on and ask about things that I hadn't mentioned in my resume or told them during the phone interview, such as virtualization and assembly programming.

If you were looking for someone who already had experience with all of those, you shouldn't have invited me for the onsite interview. Or, at the very least, don't take those things into account and see whether I can learn them or not.