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Thursday, January 12, 2006

Tweaking the Acer - Part II, ePowerManagement

One of the much touted features of the Intel Pentium M series is their ability to dynamically change processor speed in response to software demands. The upshot of this is that a laptop can 'run idle' when not connected to AC power, extending battery life. Windows XP supports SpeedStep and other power management features, but Acer provides its customers with a more advanced tool, called Acer ePowerManagement. Unfortunately, as with many Windows applications, ePowerManagement only works if the logged-in user has administrator privileges.

In UNIX, the obvious solution would be to set the SUID bit on the relevant application, but Windows has no equivalent concept, so I had to try a different avenue.

My plan was to run Acer ePowerManagement as a service. First, I downloaded the Windows server 2003 resource kit tools. I then created a service called epowermanagement by typing the following at the command prompt:
cd "C:\Program Files\Windows Resource Kits\Tools"
instsrv.exe epowermanagement "C:\Program Files\Windows Resource Kits\Tools\srvany.exe"
The service can be configured by going to
Start → Control Panel → Administrative Tools → Services
and then finding epowermanagement. Right-click for the context menu, and select properties. From the "log on" tab, select Local Account and check "Allow service to interact with desktop". In order to set the actual application to run, one needs to use regedit.

Go to
HKEY_LM\SYSTEM\CurrentControlSet\Services\epowermanagement
(where LM is short for LOCAL_MACHINE) and create a new key called Parameters. In this key create a new string, and call it Application. I changed its value to C:\Acer\ePM\EPM-DM.exe.

This is enough for most purposes, but as it is, you will see error messages of the form "Access violation at address xxxxx in module 'ePM.exe'" when connecting/disconnecting from AC power. Moreover, you will only be able to alter the settings when logged in as an Administrator. The resolution of these problems will be the topic of Tweaking the Acer - Part III.

5 Comments:

  • At 6:11 pm, Blogger Tian said…

    hi,
    im using an acer aspire 5110
    recently, i installed windows server 2003 on it
    but ePower Management does not seem to work
    all the fields in the window is blank
    however the tray icon still works, i can disable/enable wlan, lan etc from there
    wht's the problem?
    please help me out
    thanks very much!

     
  • At 9:49 am, Blogger j.treehorn said…

    Dear Tian,

    Have you tried clicking on the "Create Power Scheme" button from the ePowerManagment dialog box?

    Best,

    G.

     
  • At 10:38 pm, Blogger Gabor said…

    what is that anbmserv???

     
  • At 11:13 pm, Blogger Gabor said…

    i think "Allow service to interact with desktop" don't work in this case because epm-dm can't place icon to systray.

     
  • At 8:43 pm, Anonymous Anonymous said…

    Fuck Acer, the dickheads couldn't install their software properly so the poor old user / sysadmin has to waste their time hacking it - yet again!
    Why do wanker programmers not respect the Windows security model - including software that has to have direct hardware control but run under limited accounts. I mean, it's not like Windows NT just came out and no-one in coding is used to implementing the Windows security model, no, they're just lazy idiots.
    Trying to get this software to run correctly under a limited user account has now nuked my XP Power Control Panel. I'm using diagnostic software to get the bottom of it, but all has failed to rectify it so far (can't even OPEN it, let alone change it).

    Anyway, sorry for the offensive language, it's not aimed at anyone but the crap companies who don't pull their weight and do their job properly (Acer, now, Microsoft, Creative, Apple immediately spring to mind).

    Thanks for your attention and how-to on this subject, j.shoehorn

     

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