Les 3 "bruits" du MacBook Pro

[human]

D'aprés les forums d'apple sur le MacBook Pro, de nombreuses personnes se sont plains du bruit de cette merveilleuse machine ...

Il y a apparement 3 differents sons :

Le premier, appelé "humming noise", vient de l'ecran ... ou plus précisement de ce qu'ils appellent "the power inverter for the display" et ressemble a ça :

http://homepage.mac.com/jimdufek/mbp/movie...mming_noise.mov

D'aprés les dires de quelques personnes du forum, apple serait au courant et ferait le necessaire pour reparer ça.

Le second, appelé "squeal noise" et viendrai d'en dessous du clavier.
Il peut arriver a n'importe quel moment durer plusieurs secondes et repartir comme il est venu :

http://homepage.mac.com/jimdufek/mbp/movies/squeal_noise.mov

Le troisieme son appellé "whine sound" apparait lorsque le cpu ne fait rien:

http://woody.solivant.com:8089/macbookpro/

ATTENTION : ces 3 enregistrements ont été "boostés". Ils ne sont pas aussi fort " en vrai " mais sont audible sans pour autant déposer son tympan sur la machine .

Apparement le probleme ne vient pas du MacBook (quel horreur ce nom ...)
mais du dualcore intel .
Une personne travaillant chez intel a poster ceci :
"I used to work for Intel in the mobile computer group and this kind of idle CPU whine is a known problem. The cause is an interaction between the CPU's switching power supply, the OS X task scheduler interrupt, and the CPU low power states. OS X configures the hardware to generate a hardware interrupt at some fixed period that is probably on the order of 1kHz. If the system is idle then this interrupt causes OS X to wake up the CPUs, determine that the system is still idle, and put the CPUs back into a low power state. The net affect of this is that the current flowing from the power supply to the CPU is a square wave at some frequency on the order of 1kHz. Components in the CPU power supply are vibrating at this interrupt rate and producing audible noise.

I understand that G4 Powerbooks have this problem too, but to a much lesser extent. The Core Duo's higher active power and better low power states means that the periodic change in CPU current demand is higher with the Core Duo than it is with the G4.

This is a very hard design problem to solve. The OS needs a periodic interrupt for scheduling tasks, the CPU needs lots of current when it is busy, and good low power states need to be used when the CPU is idle to get good battery life. Some Windoze laptop vendors "solved" this problem by not using the best low power CPU states, keeping the CPU current demand at a more constant level. But Apple would never compromise battery life to save cost. Apple probably used costlier components for the CPU power supply to mitigate this problem, but I guess it wasn't enough.

The people who have noticed that running Image Capture fixes the noise problem are probably emulating the bad Windoze vendor behavior. My guess is that Image Capture causes the best CPU low power states to become unavailable (a common problem with some types of hardware), which reduces the magnitude of the periodic current change.

Why some people have this problem and others don't is probably due to the vagaries of chance and the nature of the components in their CPU power supply."

De plus d'autres personnes ayant le dualcore sur des machines non apple aurait la meme choses ...

Il y a meme un site qui répertorie les MacBook qui ont ce probleme :
http://www.schmidp.com/macbook/whine/

Il y aurait apparement 3 techniques :

- Utiliser le widget "Mirror" puis le fermer.
http://www.apple.com/downloads/dashboard/webcams/mirror.html
- Désactiver un core avec les CHUD tools.
- ne pas laisser "souffler" la machine ;-)

Désoler pour la longueur du post ... en esperant que mes recherches puisse etre profitable a d'autres .

source:
http://discussions.apple.com/thread.jspa?t...74397&tstart=15

Avez vous se genre de chose sur votre MacBook Pro ?

Ce message a été modifié par human - 10 Mar 2006, 17:11.