NCR RealPOS 40 - ACPI Sleep States (S0 - S5)

1-14 Chapter 1: Product Overview
ACPI Sleep States (S0 – S5)
UndertheG1sleepingstateACPIdefineslevelsofsystemsleepstatesupport.The
7600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hardw
aremaintainsall
systemcontexts. 
Note: The7600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sta
te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on‐boardUSB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conti
nue
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wak
e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
– Someperip
heralsmaynotbeS4capable,whichcanpreventthesystemfrom
enteringS4state.
ReferencetheACPISpecificationfordetails.