http://www.h-online.com/open/feature...x-1257057.html
New user interface
Like earlier versions of the tool, on starting up, the second generation of Powertop provides an overview of which programs engage the CPU how often and thus shorten the time the processor can remain in power-saving sleep states. In a compact overview, the program now not only displays the processor load, it also indicates how often the graphics chip (GPU/Graphics Processing Unit) became active in the previous measuring period, and how often the Virtual File System (VFS), which offers basic file system functionality, accessed the storage media.
However, the new version provides considerably more detail about the various processor cores' sleep periods, and it also shows the status of the processor package – which includes the processor cores and the "uncore" area that contains components such as the memory controller and I/O units. The information is no longer presented on the main program page but is now located in the "Idle Stats" tab, which is accessible by pressing the right cursor key. Which clock speed is being used, how often, and whether the processor also shifts to turbo boost frequencies is shown in the "Frequency Stats" tab. The "Device Stats" tab provides a device activity overview and displays the number of transmitted network packages. Devices that don't use any power-saving mechanisms are listed as being one hundred per cent active.
Fine tuning
The last tab offers "Tunables" that allow users to enable and disable specific power-saving features – such as the auto-suspend feature for USB and audio hardware. Unfortunately, it remains unknown exactly how Powertop makes this happen; ultimately, however, it tends to use the tricks described in detail at lesswatts.org.
One of the reasons why current distributions don't automatically use all the power-saving mechanisms that are accessible via Powertop is that some of them are quite recent and only work with the latest kernel versions.
Like earlier versions of the tool, on starting up, the second generation of Powertop provides an overview of which programs engage the CPU how often and thus shorten the time the processor can remain in power-saving sleep states. In a compact overview, the program now not only displays the processor load, it also indicates how often the graphics chip (GPU/Graphics Processing Unit) became active in the previous measuring period, and how often the Virtual File System (VFS), which offers basic file system functionality, accessed the storage media.
However, the new version provides considerably more detail about the various processor cores' sleep periods, and it also shows the status of the processor package – which includes the processor cores and the "uncore" area that contains components such as the memory controller and I/O units. The information is no longer presented on the main program page but is now located in the "Idle Stats" tab, which is accessible by pressing the right cursor key. Which clock speed is being used, how often, and whether the processor also shifts to turbo boost frequencies is shown in the "Frequency Stats" tab. The "Device Stats" tab provides a device activity overview and displays the number of transmitted network packages. Devices that don't use any power-saving mechanisms are listed as being one hundred per cent active.
Fine tuning
The last tab offers "Tunables" that allow users to enable and disable specific power-saving features – such as the auto-suspend feature for USB and audio hardware. Unfortunately, it remains unknown exactly how Powertop makes this happen; ultimately, however, it tends to use the tricks described in detail at lesswatts.org.
One of the reasons why current distributions don't automatically use all the power-saving mechanisms that are accessible via Powertop is that some of them are quite recent and only work with the latest kernel versions.
The "tips&tricks" on the lesswatts.org website, which was given as examples of what "tunables" are and would do, focuses entirely on saving power, except that in addition to the CPU the new version also monitors the GPU and the VFS. 
That's a serious stack of stuff to look at!
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