I'm not familiar with the tty driver in late versions of Unix like 4.1 (sic), but I'm very familiar with the one in V6, and it's not the raw mode _itself_ that caused the load (the code paths in the kernel for cooked and raw aren't that different), but rather the need to wake up and run a process on every character that was the real load. When Bernie Greenberg did EMACS for Multics, he had a similar issue. I recall reading a document with an extensive discussion of how they dealt with this, especially when using the system over the ARPANET. IIRC, normal printing characters were echoed without waking up the process; remotely, when using the network. If anyone's really interested in this, and can't find it themselves, I can try looking for it. Noel