NCR RealPOS 40 - ACPI Processor C-States

Chapter 1: Product Overview 1-21
ACPI Processor C-States
ACPIdefinesthepowerstateofsystemprocessorswhileintheG0workingstateas
beingeitheractive(executing)orsleeping(notexecuting).Processorpowerstatesare
designatedC0,C1,C2,C3,…Cn.
TheC0powerstateisanactivepowerstatewheretheCPUexecutesinstructions.The
C1throughCnpowerst
atesareprocessorsleepingstateswheretheprocessor
consumeslesspoweranddissipateslessheatthanleavingtheprocessorintheC0
state.
Whileinasleepingstate,theprocessordoesnotexecuteanyinstructions.Each
processorsleepingstatehasalatencyassociatedwithenteringandexitingthat
correspondstothepowersavings.Ingeneral,thelongertheen
try/exitlatency,the
greaterthepowersavingswheninthestate.
Toconservepower,OSPMplacestheprocessorintooneofitssupportedsleeping
stateswhenidle.WhileintheC0state,ACPIallowstheperformanceoftheprocessor
tobealteredthroughade
fined“throttling”processandthroughtransitionsinto
multipleperformancestates(P‐states).
Note: The7600AtomN270ProcessorsupportsC0andC1states.Supportofdeeper
sleepstatesisnotrequiredduetoits inherentlylowpowerconsumption.