Active Protection System

The Active Protection System

With the new series of Thinkpads IBM introduced the Active Protection System (APS) in 2003. The APS is a protection system for the Thinkpad's internal harddrive. A sensor inside the Thinkpad recognizes when the notebook is accelerated. A software applet then is triggered to park the harddisk. This way the risk of data loss in case of when the notebook is dropped is significantly reduced since the read/write head of the harddrive is parked and hence can't crash onto the platter when the notebook drops onto the floor.

The whole concept of the technology seems very advanced. For the first part, the hardware sensor is capable of not only recognizing acceleration of the notebook, but also (to a certain degree) of its whole orientation in space, relative to gravity's axis. Furthermore, having the actual control put into software, its functionality is extendable and it gives chance to implement features like the "ignore minor shocks" feature which is present in the Windows based control applet. (This feature prevents the harddrive from parking in case of minor regular shocks such as occur when in a train or car.)

Linux Support

Linux support is in early development.

This feature definitely depends on software and there is no hardware or BIOS only way of making it work. A statement from IBM clearifies this: "The APS system will require APS software to be installed on the computer before it activates the harddrive parking . This means it will not work on systems preloaded with Linux."

IBM made contradictory statements about their willingness to release the specifications of the hardware sensor and its API to the linux community or some developers. Although a lot of developers and other interested people from the OpenSource community actively contacted IBM to get the specs, in fact they never got them.

Meanwhile, some independent projects are making progress:

Quoted from NewScientist.com: The latest Apple PowerBook laptops can be controlled with a gentle shake. Programmer Amit Singh has written code that lets him use the sensor to control software on the computer. The code is published at www.kernelthread.com/software/ams/.

There is a fairly detailed article about reverse engineering the APS accelerometer interface by Mark Smith from IBM Research. Apparently they even have a prototype Linux driver working, but cannot release the full source yet.

The HDAPS project is dedicated to developing & testing a kernel module and a user space application. More info on this can also be optained from the HDAPS mailinglist and its archive. You can also find some of the coders working on this module in the #hdaps channel on irc.freenode.org.