According to Activity Monitor, Alchemy sucks up 30% the cycles on my twin 1-GHz G4 running 10.4.5, so I close the TV window when I'm not watching TV. It drops down to 0% then. I would quit the app altogether, but it can be pickly about starting up when other apps have been running: it wants to be first after boot, so sometimes a reboot is necessary. I haven't done a clean install in years and my system is no doubt filled with junk, so the pickiness is probably my fault. Overall, the card and the app are a lot of fun and include an astonishing number of features for such a niche market.