however I could dig out the references to it. Apparently it was a course by Prof. Alex Aiken and karpathy was a TA.
This repository seems to be a future version of the same course. https://github.com/gboduljak/stanford-compilers-coursework
Edit: found the videos from the course on the archive https://archive.org/details/academictorrents_e31e54905c7b266...