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View Full Version : removing PMU system file makes PB & iBooks run cooler?


cb911
Oct 31, 2003, 03:34 AM
i was just reading Tech Tails #189 and saw this...

How Hot Is That?
By Jon Spaulding

So, your PowerBook and iBook run a little warm. You've found that you can prepare Cup'o'noodle's, maybe even Ramen, on the area to the left of your Track-pad, or if you were to flip the machine, an area just short of the hinge to the right of center (when flipped). Well, this might just be the relief you need.

http://discussions.info.apple.com/WebX?128@249.7kYJaRiXjGf.0@.3bc109fc

It has been found, that the removal of a simple PMU (Power Management Unit) System file, that Apple portables seem to run a little cooler. So, how do you remove, and what file is it?

The file can be found by selecting Go in your menu bar, selecting Go to Folder, and typing in var/db/SystemPreference. That will bring you to the folder, but you will not be able to remove the file com.apple.PowerManagement.xml, simply because you do not have permission to do so.

Open up a session in Terminal. From Terminal, you will be able to remove the file by typing the following:

sudo rm /private/var/db/SystemConfiguration/com.apple.PowerManagement.xml

Hit enter. This will prompt your machine to ask for your ROOT password. Entering the password will then enable Super User do, sudo, to remove the folder.

Shut the machine down. While the machine is turned off, perform a PMU reset, Control, Option, Shift and Power. Wait five or more seconds, restart the machine. The PMU reset may force you to reset the time and date on your machine.

Secondarily, with a second mac and Tinker Tool, or other invisible/hidden folder apps, you could mount the drive of your portable via FireWire Target Disk mode, and remove the file without running into permission issues.

Or finally, Boot to single user mode and rename the file. To boot into single user mode, hold down the Apple key and 's' at Boot. From there, type the following commands:

/sbin/mount -uw /

cd /private/var/db/SystemConfiguration/

mv com.apple.PowerManagement.xml com.apple.PowerManagement.xml.backup

shutdown -h now

Before rebooting, the PMU reset is applied by holding down Control, Option, Shift and Power. Wait five or more seconds, restart the machine, and use. In this last part, we have not removed the file, but nearly renamed it.


seems safe... and people over at the Apple boards say that it works, but i'm not too sure about this?

what do people here think? to me it seems very unsafe to be messing with system files like that...

manitoubalck
Oct 31, 2003, 04:31 AM
Originally posted by cb911
what do people here think? to me it seems very unsafe to be messing with system files like that...

Well it'll more thatn likley void the warrenty if mac find out that you're having processor troubles and that you've removed the file, but life no fun unless you take the odd risk,

cb911
Oct 31, 2003, 07:28 AM
are you serious it would void the warranty?! :eek: i never even thought about that...

i guess i'll just leave this alone. i'm happy with my PB just the way it is.

stoid
Oct 31, 2003, 09:00 AM
Since my friend has fried two video cards in his nearly 2 inch thick laptop I think I'm going to leave the system just the way it is.

Vector
Oct 31, 2003, 09:42 AM
Originally posted by manitoubalck
Well it'll more thatn likley void the warrenty if mac find out that you're having processor troubles and that you've removed the file, but life no fun unless you take the odd risk,

This is not something that can void your warranty; it is simply a software hack. All this does is reset the power management settings that the computer uses. You are simply deleting the original PMU settings and then reseting them using the command and a restart. This creates a new PMU profile to replace the one that you deleted.

If you are worried about messing something up (unlikely if you follow the directions) you can create a backup of the original settings, as the instructions say, and put them back if the new settings don't seem to work.

This will not void your warranty. It is only a software change that can be reversed by replacing the recreated PMU settings file with the original or by reinstalling the os.

iJon
Oct 31, 2003, 10:14 AM
it will not void your warranty like vector said. it is just software. since it is a preference file you will just be making a brand new set, your not deletling it completly.

iJon

cb911
Nov 1, 2003, 05:41 PM
i was thinking it would be a bit strange if the warranty was void by changing a bit of software...

i'm thinking about doing this on my PowerBook. i came across this (http://docs.info.apple.com/article.html?artnum=14449#faq10) KnowledgeBase article that talks about resetting the PMU, the actual hardware circuti though.

the steps are alot shorter. this is for the new PB's :

1. If the computer is on, turn it off.
2. Reset the power manager by simultaneously pressing and then releasing Shift-Control-Option-power on the keyboard. Do not press the fn (Function) key while using this combination of keystrokes.
3. Wait 5 seconds.
4. Press the power button to restart the computer.

if removing the PMU preference file only creates a new one (basically the same as resetting the pref file), what's the difference between resetting the hardware and removing the PMU pref file?

aren't these two methods describing how to accomplish the same thing? or have i missed something?

beefcake
Nov 1, 2003, 06:33 PM
That article makes resetting the PMU seem like a last resort bug fix to be avoided. I don't really care how hot my PB gets, but if it is running cooler, would it be correct to assume that the rather noisy fan wouldn't run as frequently?

Vector
Nov 1, 2003, 06:44 PM
Originally posted by beefcake
That article makes resetting the PMU seem like a last resort bug fix to be avoided. I don't really care how hot my PB gets, but if it is running cooler, would it be correct to assume that the rather noisy fan wouldn't run as frequently?

It really isn't that big of a deal. as cb911 mentioned you can just perform a standard PMU reset which should yield the same or nearly the same results as the process previously described.