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.