I just finished the written portion of my PhD comprehensive exam. They were actually quite excellent exams. The questions were way more open-ended than I expected. I spent 6.5 hours writing the first two days, 5.5 hours the third day and 10 hours today. I could have written a LOT more. The cool diagram above is one I created to describe the hardware for the system I designed as part of my research–but I am not a hardware guy so I do not have much of a clue about that. I mostly just wrote the software and designed the vision algorithms.