Mac OS X 10.6: Checking your computer’s performance
You can keep an eye on your computer’s performance by using the Activity Monitor application to monitor your computer’s processor activity, hard disk usage, memory, and network activity.
Activity Monitor displays various aspects of your system’s performance using graphs and numbers. For example, if you use applications that require a lot of processor power, such as graphics, video editing, or rendering, you can see how much of a demand the applications are placing on your computer’s processor.
Activity Monitor can display this activity in the Dock, making it easier for you to quickly check on your computer’s performance.
For more information on Activity Monitor, open Activity Monitor and choose Help > Activity Monitor Help.