Note, in all cases the system is shut down to some extent, so it can do no useful work. Depending on settings entry into or recovery from these sleep states can be automatic or manual, but in the case of downloads it is unlikely that the system would be sufficiently idle to ever enter one of these modes. However, it is possible to shut off the monitor, and possibly some disk drives (if you have more than one) to reduce power consumption, and the prog indicated by Withcheese would reduce power usage at other times.Sleep States
S1 - "Stopgrant"
Power to cpu is maintained, but no instructions are executed. The CPU halts itself and may shut down many of its internal components. In Microsoft Windows, the "Standby" command is associated with this state by default.
S2
While defined in the spec, this state is not currently in use. It resembles S3 with the qualification that some devices are permitted to remain on.
S3 - "Suspend to RAM"
All power to the cpu is shut off, and the contents of its registers are flushed to RAM, which remains on. In Microsoft Windows, the "Standby" command can be associated with this state if enabled in the BIOS. Because it requires a high degree of coordination between the cpu, chipset, devices, OS, BIOS, and OS device drivers, this system state is the most prone to errors and instability.
S4 - "Suspend to Disk"
CPU power shut off as in S3, but RAM is written to disk and shut off as well. In Microsoft Windows, the "Hibernate" command is associated with this state. A variation called S4BIOS is most prevalent, where the system image is stored and loaded by the BIOS instead of the OS. Because the contents of RAM are written out to disk, system context is maintained. For example, unsaved files would not be lost following an S4 transition.
S5 - "Soft Off"
System is shut down, however some power may be supplied to certain devices to generate a wake event, for example to support automatic startup from a LAN or USB device. In Microsoft Windows, the "Shut down" command is associated with this state. Mechanical power can usually be removed or restored with no ill effects.
Reply With Quote
Bookmarks