Aggressive Link Power Management (ALPM)
AHCI Link Power Management
AHCI Link Power Management is a mechanism where the SATA AHCI controller puts the SATA link to the internal HDD and/or SSD disk into a very low power mode when there's no IO (input/output) activity for a while. The controller automatically puts the link back into active power state when there's real work to be done. This is done to save power consumption by the HDD and/or SSD disk. Tests show that this can save around 0.4 Watts of power and decrease mSATA average temperature.
- HIPM = Host Initiated Link Power Management
- DIPM = Device Initiated Link Power Management
Windows
Enabling and disabling AHCI Link Power Management in Windows:
The Link Power Management option is hidden/disabled by default in Windows advanced power options, and it is required to add the support into Windows registry:
- Adding the AHCI Link Power Management – HIPM/DIPM option to Advanced Power Settings.
- Download the Add_LPM.reg (Right click and Save link as...).
- Right click on the downloaded Add_LPM.reg file and click on Merge.
- After the success message appears, restart the unit.
- Removing the AHCI Link Power Management – HIPM/DIPM option from Advanced Power Settings.
- Download the Remove_LPM.reg (Right click and Save link as...).
- Right click on the downloaded Remove_LPM.reg file and click on Merge.
- After the success message appears, restart the unit.
- Configuring the AHCI Link Power Management – HIPM/DIPM option in the Advanced Power Settings.
- Click on the Start button.
- Type Power Options in the Start search box and press Enter.
- In the Power options window, click on the Change plan settings of the current power plan.
- In the Plan Settings window, click on the Change advanced power settings.
- In the Advanced Plan Settings click on the Hard disk option and expand it.
- The following settings are responsible on the AHCI Link Power Management:
- AHCI Link Power Management – HIPM/DIPM. It will set the Link Power Management policy:
- Active: Neither HIPM or DIPM allowed
- HIPM: HIPM only is allowed
- HIPM+DIPM:HIPM and DIPM are allowed
- DIPM: DIPM only is allowed
- Lowest:HIPM, DIPM and DEVSLP are allowed (if DEVSLP is supported by the storage device).
- AHCI Link Power Management – Adaptive. It will set the period of AHCI link idle time before the link is put in the slumber state when you have HIPM, DIPM, HIPM+DIPM or Lowest set above. It can be set to be from 0 to 300,000 milliseconds. If the Active is set above, then this will have no effect.
- AHCI Link Power Management – HIPM/DIPM. It will set the Link Power Management policy:
Linux
Enabling and disabling AHCI Link Power Management in Linux:
- Create text file /etc/pm/power.d/sata_alpm
#!/bin/sh for i in /sys/class/scsi_host/host*/link_power_management_policy; do echo min_power > $i done
- Make it executable
$ sudo chmod +x /etc/pm/power.d/sata_alpm
- Reboot, check that SATA power management policy have been changed
$ cat /sys/class/scsi_host/host*/link_power_management_policy min_power min_power