[TUHS] vi in cooked mode?

I remember being told back in the 1980s that vi would set the terminal to "cooked mode" when vi was in "insert mode", so as to reduce expensive context switching for each character typed. Only vi's "command mode" would set the terminal to "raw mode" so as to provide immediate feedback on each (command) character typed. This would be a clever system performance optimization, and would also explain designing vi around distinct insert and command modes. However, I can't find such evidence even as far back as BSD 1. It seems that in insert mode ESC was processed like any other character. https://github.com/dspinellis/unix-history-repo/blob/BSD-1-Snapshot-Develop… Cooked mode was only entered when scrolling in order to receive interrupts. https://github.com/dspinellis/unix-history-repo/blob/BSD-1-Snapshot-Develop… Also, for this scheme to work ESC would need to be mapped to an interrupt key, so as to allow exiting the cooked mode through the corresponding signal handler. Again, grepping for ESC, did not show me any such code. I also remember being told that this optimization was what allowed twenty students to concurrently perform interactive editing on a VAX 11/780 (running 4.2BSD and then 4.3BSD), and that Emacs was not provided to students because it was always operating in raw mode. Was I misled? Was there perhaps a hacked version of vi that worked in this way? -Diomidis