Ever since I installed X last September, I have been very bothered by the fact that if I went to an OS 9 mac and mounted a volume from my OS X mac via file sharing, everything from mounting the volume to opening windows to scrolling through a window was incredibly slow.
Yesterday I unchecked "Enable File Sharing clients to connect over TCP/IP" in the File Sharing Control Panel in Classic on my OS X mac, and now file sharing is as it should be. Why having that checked in Classic would have such an effect even when File Sharing was turned off in Classic is a mystery to me.
[Editor's note: I have not tested this here, as I haven't had any speed issues with file sharing. On my OS X box, however, my "optimized Classic" environment doesn't even load any of the file sharing bits, so perhaps that's why I haven't noticed a problem. Can any of the readers verify this as a potential fix for the problem?]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020401093745163