7-128 Power Management
G0 Working
A computer state where the system dispatches user mode (application) threads and they
execute. In this state, peripheral devices (peripherals) are having their power state
changed dynamically. The user can select, through some UI, various performance/power
characteristics of the system to have the software optimize for performance or battery
life. The system responds to external events in real time. It is not safe to disassemble the
machine in this state.
ACPI Sleep States (S0 - S5)
Under the G1 sleeping state ACPI defines levels of system sleep state support. The CX5
supports the following sleeping states:
• S0: Normal Powered-On state
• S1 (Standby): The S1 sleeping state is a low wake latency sleeping state. In this state,
no system context is lost (CPU or chip set) and hardware maintains all system
contexts.
Note: The CX5 does not support S1 state. Turning off the backlight and hard drives
provides the equivalent power savings (due to Intel's processor C-states feature) at
nearly zero latency.
• S2: Not supported
• S3 (Suspend to Ram): The S3 sleeping state is a low wake latency sleeping state. This
state is similar to the S1 sleeping state except that the CPU and system cache context
is lost (the OS is responsible for maintaining the caches and CPU context). Control
starts from the processor's reset vector after the wake event. In NCR systems, during
S3, power is only provided to the USB 3.0 ports.
Note: When the terminal resumes from an S3 state, all the USB devices re-
enumerate. This causes speaker tones as if they were disconnected and then
reconnected. This does not present a problem and the USB devices will continue to
operate correctly.
Requirements for S3 support:
• O/S must be built on a system with S3 enabled in the BIOS
• Some peripherals may not be S3 capable, which can prevent the system from
entering S3 state.
• S4 (Suspend to Disk): The S4 state is the lowest power, longest wake latency
sleeping state supported by ACPI. In order to reduce power to a minimum, it is
assumed that the hardware platform has powered off all devices. Platform context is
maintained.
Requirements for S4 support:
• O/S must be built on a system with S3 enabled in the BIOS
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