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Mac OS X and Battery Life

by Derrick Story
05/15/2001

In a recent article, The Disaster-Free Upgrade to Mac OS X, I mentioned my disappointment in the power management capabilities of Mac OS X 10.0.1. Things seem to have improved a bit with releases 10.0.2 and 10.0.3, but there still seems to be room for improvement.

I received a note from Peter Fraterdeus, who is a longtime Mac user, developer, and Linux webmaster, saying that he had some insights into the battery drain problem on laptops running early versions of Mac OS X. Peter ran some tests and was willing to share his discoveries with the O'Reilly audience. So, take it away Peter ...

Keep it Cool

In Derrick's recent article about how to upgrade your system to Mac OS X, one of his "bow-wows" about OS X was: "My battery drains faster! I hate that! My previously 4-hour PowerBook battery now only lasts about two and a half hours."

I'd like to share here a few pointers and tips to help PowerBook users understand some of the concerns specific to the portables running OS X.

Of course, you should make a point of checking Apple's Mac OS X site regularly, or allow your Software Update panel to install the latest updates (as of this writing, we're at 10.0.3).

I expect that Derrick will have less of a problem after the first two updates are installed. The battery life was hit very badly by instability in NetInfo. Although it seemed to be fine when you'd first boot up, after switching to a different Location (Network Preference or under the Apple Menu), it would spend all available processor cycles trying to reconnect to a missing server, creating a power-hungry process and a far-hotter processor. [1].

However, even through NetInfo is now less greedy, it's still not unusual to have the processor running with the pedal to the metal, not only draining the battery and overheating the CPU, but also contributing to the perception that the system is less responsive than it should be. (Desktop machines will, of course, be affected by this too!)


Screenshot of CPU monitor -- click for larger view.
You can find the CPU Monitor in your Mac OS X Applications folder under Utilities (Click for larger view).

I've put the little CPU Monitor floating window up in the top right of my screen. This lets me note right away if a process is sucking more than its share of power. It doesn't tell me which process is doing the sucking, however. For this, we'll use some of our wizard tools and look under the hood for the culprits!

Comment on this articleAre you noticing a power management improvement with Mac OS 10.0.3? What other observations do you have?View and post comments..

The Extended Display shows the relative use by System vs. User processes. In this case, you can see that the User processes are absorbing the entire remaining horsepower of the CPU.

As I was reading one of my (excessive) Mac OS mailing lists late at night, I noticed a repeating disk access about happening about once a second. There are a couple of methods to track down what's causing this. It's not likely that a recurring access is a normal situation, and certainly not if your Apple notebook is not plugged in.

This kind of thing will cause your battery to evaporate like brandy in a hot saucepan! By watching the current processes in the Terminal using top -u, you can see exactly which process is firing up (the -u option sorts the list by processor usage. Try man top for more details).

In this case, I can see the LaunchCFMA process is popping up at the same time the disk is being accessed. However, this LaunchCFMApp is a system process that is used by other applications to start a Carbon application that uses the Code Fragment Manager API.

The command ps auwww (pshawww?) shows the current snapshot of the process list. The extra ws force the entire path of the process to show instead of being truncated at the window width.

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