Hardware Reference
In-Depth Information
When the system is idle (no keyboard or mouse input) for a preset period, the system
enters the Global G1 (Sleeping) state, which means also selecting one of the S1-S4 sleep
states. In these states, the system appears to be off, but all system context and status are
saved, enabling the system to return to exactly where it left off, with varying amounts of
latency. For example, returning to the G0 (Working) state from the G1/S4 (Hibernation)
state requires more time than when returning from the G1/S3 (Suspend) state.
When the user presses the power button to turn the system off or selects Shutdown via the
OS, the system enters the G2/S5 (Soft Off) state. In this state, no context is saved, and
the system is completely off except for standby power. Fully disconnecting AC or battery
power causes the system to be in the Global G3 (Mechanical Off) state, which is the only
state in which the system should be disassembled.
During the system setup and boot process, ACPI performs a series of checks and tests to
see whether the system hardware and BIOS support ACPI. If support is not detected or is
found to be faulty, the system typically reverts to standard Advanced Power Management
control,whichisreferredtoas
legacy power management
underACPI.VirtuallyallACPI
problems are the result of partial or incomplete ACPI implementations or incompatibilit-
ies in either the BIOS or device drivers. If you encounter any of these errors, contact your
motherboard manufacturer for an updated BIOS or the device manufacturers for updated
drivers.
Power Cycling
Should you turn off a system when it is not in use? To answer this frequent question,
you should understand some facts about electrical components and what makes them fail.
Combine this knowledge with information on power consumption, cost, and safety to
come to your own conclusion. Because circumstances can vary, the best answer for your
own situation might be different from the answer for others, depending on your particular
needs and applications.
Frequentlypoweringasystemonandoffdoescausedeteriorationanddamagetothecom-
ponents. This seems logical, but the simple reason is not obvious to most people. Many
believe that flipping system power on and off frequently is harmful because it electrically
“shocks” the system. The real problem, however, is temperature or thermal shock. As the
system warms up, the components expand; as it cools off, the components contract. In ad-
dition, various materials in the system have different thermal expansion coefficients, so
they expand and contract at different rates. Over time, thermal shock causes deterioration
in many areas of a system.
From a pure system-reliability viewpoint, you should insulate the system from thermal
shock as much as possible. When a system is turned on, the components go from ambient
