Waking a Sleeping PowerBook

I’ve started working on my project to measure PowerBook battery life given various workloads.

The battery lasts so long that it’s going to take a while to get a lot of different measurements, but so far I have two: 2 hours 51 Minutes with the usage set to Normal, screen at full brightness, disk drive awake (being accessed at regular intervals), with the screen saver running, and 2 hours 56 minutes (so four more minutes) for the same configuration, but with no disk access.

So sleeping the hard disk results in almost 3% longer battery life.

One of the things that makes Apple products so attractive is the attention to engineering details, and I just ran across another one. At the end of the second test, the OS must have noticed it was low on juice and put the machine to sleep. The sleeping Mac continues to use power, but at a much lower rate. I’m not sure how much lower (or how to measure it – any ideas?) but my Mac apparently got into a state where it was sleeping, and knew it didn’t have enough power left to wake up.

So it was animating the light on the front button (to indicate it was sleeping) but wouldn’t wake up until I attached the power adapter, at which point it woke up.

Nice touch.