Occasionally, I still need to run some apps in Classic. When I do, it's annoying that Classic uses a good chunk of my CPU (30%-60%) even when it's in the background doing nothing. One fix for this is to pause Classic by sending the TruBlueEnvironment process a stop signal, like so:
killall -STOP TruBlueEnvironment
This will pause Classic so that it doesn't eat your CPU. When you're ready to use Classic again, unpause it by doing this:
sudo killall -CONT TruBlueEnvironment
You have to use sudo because attempting to restart the process as a regular user will result in an "Operation not permitted" error. I haven't yet been able to figure out why this is.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20050712175556873