From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758318AbXGHMCB (ORCPT ); Sun, 8 Jul 2007 08:02:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757177AbXGHL5g (ORCPT ); Sun, 8 Jul 2007 07:57:36 -0400 Received: from viefep18-int.chello.at ([213.46.255.22]:31485 "EHLO viefep17-int.chello.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1757126AbXGHL5e (ORCPT ); Sun, 8 Jul 2007 07:57:34 -0400 Date: Sun, 8 Jul 2007 13:58:14 +0200 From: Carlo Wood To: Tim Hull Cc: Henrique de Moraes Holschuh , Gerald Britton , Alan Stern , linux-kernel@vger.kernel.org Subject: Re: PROBLEM: MacBook makes whining noise when usb-uhci active Message-ID: <20070708115814.GA17462@alinoe.com> Mail-Followup-To: Carlo Wood , Tim Hull , Henrique de Moraes Holschuh , Gerald Britton , Alan Stern , linux-kernel@vger.kernel.org References: <9a7c669e0707071551v2705320dn876ad208fa60a537@mail.gmail.com> <20070708025457.GA2822@zante.sekrit.org> <20070708042712.GC12052@khazad-dum.debian.net> <9a7c669e0707072141i7d0f6f65r8cdeee908202620d@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9a7c669e0707072141i7d0f6f65r8cdeee908202620d@mail.gmail.com> User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jul 08, 2007 at 12:41:55AM -0400, Tim Hull wrote: > After reading the ThinkPad wiki link, I've found that the problem has > to do with the C3 and C4 ACPI states. I'm guessing that the 2.6.18 > kernel I was using on Debian Etch just happened to not support full > power management on my MacBook - hence, the problem didn't occur. > > Sorry for all of this - I guess I'll pass this info on to Apple and > see if they may be able to fix this with a firmware update (it occurs > on OS X too). The most likely source of a noise as you seem to describe is a ceramic capacitor. An alternative is some coil, but that you usually only hear in cases where a high frequency is used inside a voltage convertor (in order to reduce transformator or coil sizes) and I doubt that anything like that is possible in a laptop... I'd have the hear the actual sound to know what it is. 99% chance it's a ceramic capacitor that has to absorb some pulsed current. If you'd replace the capacitor with another one of a different type (same capacity, of course), for example a styroflex one, then the noise would go away. It's very difficult to find out which it is however ;). The only method that I know is by touching each capacitor (ie with pliers) while it is making noise, which will cause the sound to change a little if you have the right one. -- Carlo Wood