MacSnail

MacSnail is a Control Panel, its purpose is to slow down the Macintosh. Slowing down will prove useful to developers, to check how an application behaves. You can emulate a "small Mac" on a fast one, while keeping full access to your development tools (debugger, etc.). You may even slow down a lot to watch more easily how a window or a complex dialog box is drawn.

MacSnail doesn't install any patch, it will not slow down the Mac at all when it's "off".