SATA Aggressive Link Power Management (ALPM) - call for testing

Tim Gardner tim.gardner at
Tue Dec 6 17:14:33 UTC 2011

On 12/06/2011 06:25 AM, Colin Ian King wrote:
> Hi there,
> Aggressive Link Power Management (ALPM) is a mechanism where a SATA AHCI
> controller can put the SATA link that connects to the disk into a very
> low power mode during periods of zero I/O activity and into an active
> power state when work needs to be done. Tests show that this can save
> around 0.5-1.5 Watts of power on a typical system.
> ALPM is now available in several SATA controllers that use the Advanced
> Host Controller Interface (AHCI). However, there is some anecdotal
> evidence that some controllers may go into a low power state incorrectly
> and this ends up causing data loss. Ubuntu has the ability to use ALPM
> but it it disabled by default since it can cause data loss on some
> machines.
> We are looking for (brave?) volunteers to test ALPM for 2 reasons:
> 1) help to identify typical power savings on a range of machines
> 2) help to identify chipsets (and machines) where ALPM works reliably
> and also where it is broken and needs fixing.
> An ALPM crowd-sourcing testing Wiki page has been created that describes
> a testing methodology and has a table for test results:
> Please note that there is a possibility that ALPM MAY CAUSE DATA LOSS on
> some machines, so please ensure you have backed up your data or don't
> mind the risk in losing your data.
> Colin

How about screen backlight management? I've noticed that my screen at 
full brightness consumes about 4W compared to screen off. Should we at 
least be measuring that ?

Tim Gardner tim.gardner at

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