O'Reilly: Reducing Power Consumption on Your Linux [Laptop] BoxDec 02, 2000, 20:04 (0 Talkback[s])
(Other stories by Daniel Bovet, Marco Cesati)
"Hardware is evolving quickly and both operating system designers and end users must keep up with these rapid changes. In this short paper, we'll show how Linux is evolving to support the many hardware circuits used to track power consumption and to monitor hardware, and how the end user may take advantage of them."
"The Linux kernel doesn't directly interact with the power-management chips of IDE controllers. Therefore, you'll not find any mention of the IDE time-out in the Linux source code or in the configuration options of your kernel. However, you can set the power-management options of your IDE disk by means of an external system command named hdparm. It must be executed with super-user privileges because it chats directly with your IDE controller by reading and writing in its I/O ports."
"Even user-level applications may implement power-saving features. For example, the command: xset s 60 instructs the X Window Server to switch off the screen if the server itself remains inactive for 60 seconds. No hardware timer is directly involved here, since the server receives any keypress and thus can implement the time-out mechanism on its own. Moreover, the Linux kernel is not aware of what is going on because the X server handles the graphics card directly."