Power saving is a handy feature designed to save electricity as well as wear and tear on your PC's components. It periodically turns off various bits of PC hardware without actually shutting down the entire PC, which still runs in the background. Usually "waking up" a PC in this state causes everything to power back up, and you can resume where you left off.
In most instances, the best form of power saving is to turn off the screen, because it consumes a lot of electricity. SUSE Linux can be set so that the screen powers down after a certain period of inactivity—perhaps if you leave your desk to attend to another matter.
A standard CRT monitor (not a TFT flat-panel screen) consumes around 40 to 60 watts of electricity. This is the same amount as a household light bulb. You wouldn't leave a light switched on unnecessarily, so why leave your monitor switched on when your PC is not in use?
The power-saving features are once again accessed through the Control Center. Start the Control Center from the K menu, click the Power Control, and then click the Display Control icon on the left side of the screen. Here, you can alter various settings for powering down your monitor, as shown in Figure 10-11. Not all the modes are supported on all monitors but the most useful is the Power Off After setting. Try dragging this to around 15 minutes.
Figure 10-11. Altering power-saving features avoids wear and tear on your PC components and saves electricity.
In addition to the screen setting, you can set the power-saving mode for the entire machine. Mostly, this means the hard disk is temporarily spun down but, depending on the age of your PC, you can also set to throttle (slow down) the CPU during periods of inactivity. These options are intended to reduce the wear on your PC's components, as well as to save electricity.
This feature is also found in the Control Center. If you're on the Display Control screen, click the Back button to return to the initial Control Center screen, and then select YaST2 Modules. Click Misc, and then click Power Management. The changes you make here will apply to the entire system, not just your user account, so you'll need to click the Administrator Mode button and enter your root password.
Many of the settings here apply to only relatively modern PCs that have Advanced Configuration and Power Interface (ACPI) support.
Even if you happen to know that your PC has ACPI support, there's no guarantee SUSE Linux will support it. ACPI is a relatively new feature in the Linux kernel. At the moment, support for all types of hardware is a little shaky.
There are effectively three settings to choose from for both AC-powered and battery computer use (you can ignore the battery choices on a desktop PC): Acoustic, Powersave, and Performance. Unfortunately there's not much explanation given of what each does. Powersave is probably the best choice for the average PC, but if you must have your PC running at full speed all the time, even when you're not using it, consider the Performance setting.
You can edit each setting by clicking the Edit Schemes button. Here, you can select which kinds of overall power-saving features you would like to enable. For example, you can select to run your PC at a quiet setting, which limits performance so that less heat is generated, and therefore the system fans won't spin too fast, generating noise. If your CPU is compatible, you can also select to throttle the speed of the CPU during quiet periods, or alternatively, ensure it's kept running at full speed all the time.