He worried; his advisor begged the hw professor to give him an oral exam in place, because he was a promising candidate with a faculty job already lined up and incredible published results.
Unlike Wein, the hw professor was happy to oblige and created a basic oral exam, suspecting that the student was destined for greatness.
The student desperately tried to cram the hw textbook, but his heart was simply not into the subject. He did however, get the main point of the entire field.
This is when the funny part of the story begins. If you know this person, you know that he is remarkably clever, charming and convincing. He tells me that the hw professor had prepared a small number of questions, all beginning with something like, "explain how a XXX works in a YYY architecture", and that he really didn't know any details of XXX.
He started by copying a basic diagram of a processor onto the board. He kept his answers short, he began each with quizzical look indicating that the question was obvious, and all answers included a remark along the lines of "Obviously, its for performance!" In some cases, while facing the professor, he would point backwards to a spot between components in the diagram. He would slowly move his finger to different areas based on the look on the professor's face.
The hw professor was amused and obviously passed the candidate!
TLDR: don't let classes get in the way of your education.