Mokoi
This may help investigations ..
In Windows the task manager (Ctrl+ALt+del) > processes shows you the CPU usage by process my idle comes in at around 25% in Vista
As for Macs Click on the "Applications" icon in the a Mac "Finder" window and scroll down to the "Utilities" folder and select "Activity Monitor." Double-click "Activity Monitor" to launch the application.
And in Linux/Unix, you can use "top" (type it in a terminal). This also works for MacOSX since it's based on Unix.
Ryzom usually takes 94 - 100% of one CPU core and (depending on my in-game settings), 30 - 37% RAM.