I had a total of 3 phone interviews. They were all conducted by potential bosses. I ended up being hired to join the first interviewer's team. All the interviews started off with several personal questions (going over the resume and past experiences, what you're passionate about and what you're like as a person) before getting into the technical questions. The technical questions were all asked in increasing levels of difficulty. So if you answered the initial question off the bat, they would change something about the question to make it harder until you can't answer it anymore (or if you do, well done!) For the last interview, I had to email the answer to a technical question as complete code. The other interviews just required me to clearly explain the algorithm on the phone. They did ask the question "Why do you want to work for Nvidia?". I recommend having a clear answer in your head before the interview, be up to date about their recent developments and be really confident and show your passion. Because it's a phone interview, it wouldn't be a bad idea to have those key points listed on a post-it or something in front of you. It'll help keep you on track on why you want to get this job!