Reference Guide

To help clarify memory volatility and data retention in situations where the system is put in different ACPI power states, the

following information is provided regarding ACPI power states S0, S1, S3, S4, S5:

S0 state is the working state where the dynamic RAM is maintained and is read/write by the processor.

S1 state is a low wake-up latency sleeping state. In this state, no system context is lost (CFPU or chip set) and hardware maintains

all system contexts.

S3 is called “suspend to RAM” state or stand-by mode. In this state the dynamic RAM is maintained.

S4 is called “suspend to Disk” state or “hibernate” mode. There is no power in this state. The dynamic RAM is not maintained if the

system has been commanded to enter S4. The OS will write the system context to a non-volatile storage file and leave appropriate

context markers. When the system is coming back to the working state, a restore file from the non-volatile storage can occur. The

restore file must be valid. Dell system will be able to go to S4 if the OS and the peripherals support S4 sate.

S5 is the “soft” off state. There is no power. The OS does not save any context to wake up the system. No data will remain in any

component on the system board, i.e. cache or memory. The system will require a complete boot when awakened. Since S5 is the

shut off state, coming out of S5 requires power on which clears all registers.

The following table shows all the states supported by the PowerEdge T40

Model Number

Dell PowerEdge T40

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