Monit

Monit 1.0

Free
It allows you to see key performance data for your Mac quickly.
 
2.0 (See all)

Monit is handy application that allows you to see key performance data for your Mac quickly, such as CPU, memory, disk, network, and battery. All you need to do is click the charts to drill down and reveal more details. You can click the network and disk icons to see even more details.

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