Power Savings and Performance Modes on Ubuntu System

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http://askubuntu.com – This might be the only thing I miss from windows. There is no way to tell the system to run in high performance mode or in power saver mode. May be this feature which is already there and I am not sure. So, Is there a way to change the system operation mode into high-performance? Basically, over burning the rams and processors enabling to do several power effective task like running two OSes on VMWare and not having any performance degradation. Or, changing the system's mode into power-saver mode affecting the battery life my a lot? P.S: I dont think what can of hardware I have has (HowTos)