State 7 refers to a power saving mode or sleep state for computers and other electronic devices. It is one of the system power states defined in the Advanced Configuration and Power Interface (ACPI) specification. ACPI is an open standard that operating systems use to manage power consumption and sleep states in computers.
When a device enters state S7, it has powered off all of its components except for the RAM. This allows the device to conserve energy but quickly resume normal functioning when needed. State 7 is a deeper sleep state than standby (S3) where some components remain powered on, but it is not as deep as hibernation (S4) where RAM contents are saved to disk before fully powering down.
Some key facts about ACPI state 7:
- Also referred to as “soft off” state
- CPU and other system components are powered off
- RAM remains powered on to store system context for faster wake up
- Requires pressing power button or other wake event to exit state 7
- Lower power consumption than standby or hibernation states
Understanding the different sleep states like S7 allows for better power management and utilization of energy saving features in computers and devices.
ACPI Sleep State Definitions
The Advanced Configuration and Power Interface specification defines several system power states for managing power consumption, including:
| State | Name | Description |
|---|---|---|
| S0 | Working | Normal working state, components powered on |
| S1 | Sleeping | CPU stopped, RAM refreshed, can resume quickly |
| S2 | Sleeping deeper | Deeper sleep, lost system context |
| S3 | Standby | RAM powered on to store system context |
| S4 | Hibernation | RAM contents saved to disk, powered off completely |
| S5 | Soft off | Hardware powered off, only limited functions remain on (e.g. wake events) |
| S6 | Hard off | Full hardware power off, also called G2/Mechanical Off |
| S7 | Soft off | CPU and components powered off, RAM remains on |
As this table shows, S7 is a soft off state where RAM stays powered on but other hardware shuts down. This allows for faster wake capabilities than hibernation or full off.
Advantages of State 7
Using state 7 “soft off” sleep mode has several advantages:
Energy Savings
With the CPU, motherboard, and other components powered down, S7 offers significant energy savings vs standby or hibernation. It consumes less than 5% of normal S0 working power usage.
Faster Wake Up
Since RAM remains powered, the system can resume where it left off much faster than hibernation which has to read data from disk. Typical wake times from S7 are under 10 seconds.
Better Battery Life
The lower power draw in S7 translates directly to extended battery life on laptops and tablets. Devices can sleep in S7 much longer than standby on a single charge.
Context Retained
With RAM still active, all application context is retained allowing instant resume back to where the user left off. Other sleep states lose context (S1, S2) or save to disk (S4).
Disadvantages of State 7
While S7 has its benefits, there are also some downsides to consider:
Higher Power than Hibernation
S7 consumes more power than hibernation mode since RAM remains active. For longest battery life, S4 hibernation may be preferable.
Data Loss Risk
If power is completely interrupted, data in RAM will be lost. Sudden power failure could cause data corruption. The risk is lower than in standby.
No Automated Transition
Operating systems do not automatically transition to S7 unlike standby – it requires manually shutting down to soft off state.
Wake Events Needed
Trusted wake events like power button are needed to exit S7. Automated wake alarms cannot wake from soft off state.
Transitioning to State 7
On most PCs and laptops, S7 soft off is engaged by shutting down the device. Modern operating systems support an S7 shutdown process:
Windows
– Select Start Menu > Power > Shut Down.
– This will initiate a graceful S7 shutdown sequence.
macOS
– Go to Apple Menu > Shut Down.
– macOS will enter S7 soft off at shutdown.
Linux
– Use the “poweroff” or “shutdown” command in a terminal window.
– Most Linux distros will go to S7 when powering down.
Chromebooks
– Click system tray icon and select Power > Shut Down.
– Chromebooks enter soft off S7 at shutdown.
So for most systems, normal shutdown will engage the efficient S7 state.
Comparison to Other Sleep States
How does S7 compare to standby and hibernation power states?
| State | Power Usage | Wake Time | Context Retained? |
|---|---|---|---|
| S3 Standby | Moderate | Fast (seconds) | Yes |
| S4 Hibernation | Very Low | Slower (10s of seconds) | Yes |
| S7 Soft Off | Extremely Low | Fast (under 10 seconds) | Yes |
As the table shows, S7 offers a balance of very low power usage while still retaining context for fast wake. This makes it preferable over standby or hibernation in many usage scenarios.
Real World Usage of State 7
Many modern devices take advantage of S7 soft off capabilities:
Laptops and Tablets
Portable devices leverage S7 for battery preservation when powered down. Windows and macOS laptops enter S7 when shut down.
Smartphones
iOS and Android phones use a similar deep sleep mode to S7 when powered off for extended battery life.
Gaming Consoles
The PlayStation 5, Xbox Series X/S, and Nintendo Switch all utilize S7-like low power modes when “turned off” while plugged in. This allows fast resume of games.
Smart Home Devices
Internet-connected smart home gadgets like Google Home and Amazon Echo devices can enter an ultra-low power state similar to S7 when not actively in use. This allows them to always be listening for wake commands.
So the S7 sleep state powers the convenient and responsive sleep/wake functionality of many modern electronics we use daily.
Conclusion
State 7 or “soft off” refers to an ultra low power sleep mode where devices power down components while retaining RAM state. This allows efficient power savings alongside fast wake up capabilities. S7 offers advantages over standby and hibernation sleep modes for many usage scenarios. All major operating systems support seamless transition to and from S7 during standard shutdown and startup procedures. As electronics continue to adopt more aggressive power management, expect S7 to play an increasing role in extending battery life and delivering ideal standby behaviors.
