During the years, I have run Mac OS 10.4 on a lot of Mac hardware. Starting from my old iMac G3 DV SE (400 Mhz) up to my PowerMac G5 (late 2005). I’ve always been satisfied with the performance, probably because I usually put as much RAM into my Macs than they can take. It is a commonplace that OSX Tiger needs lots of RAM and if you feed it right, it will run nicely even on old G3 machines.
Another way to significantly improve the performance on those old machines is a utility called “shadowkiller”. The name basically says what it does – it eliminates all the fancy shadows that OSX draws around it’s windows, thus improving the overall performance. Everything becoming 2D might be a bit irritating, especially when you’re working with many windows (feels like a flashback to the early 1990s) but then again it really speeds up things. And best of all, whenever you feel like getting the shadows back you simply double click the program’s icon again and they’re all back.
I recommend using shadowkiller with G3 and early G4 machines. Putting it as a startup item in your system preferences –> users will even safe you the hassle of activating it manually after every startup.
Download shadowkiller here.