From owner-freebsd-questions@FreeBSD.ORG Tue Jun 10 01:59:49 2008 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id F36B2106566C for ; Tue, 10 Jun 2008 01:59:48 +0000 (UTC) (envelope-from chris@monochrome.org) Received: from mail.monochrome.org (b4.ebbed1.client.atlantech.net [209.190.235.180]) by mx1.freebsd.org (Postfix) with ESMTP id 854618FC13 for ; Tue, 10 Jun 2008 01:59:48 +0000 (UTC) (envelope-from chris@monochrome.org) Received: from [192.168.1.11] ([192.168.1.11]) by mail.monochrome.org (8.14.2/8.14.2) with ESMTP id m5A1xckc051533; Mon, 9 Jun 2008 21:59:38 -0400 (EDT) (envelope-from chris@monochrome.org) Date: Mon, 9 Jun 2008 21:59:38 -0400 (EDT) From: Chris Hill To: Bob McConnell In-Reply-To: Message-ID: <20080609212335.M52086@tripel.monochrome.org> References: <7039ada60806082040s36afc2c8n4698402ac5d4ff29@mail.gmail.com> <20080609111200.75197d59@epia-2.farid-hajji.net> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: James , cpghost , freebsd-questions@freebsd.org Subject: RE: Whine when EHCI controller enabled in BIOS X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 10 Jun 2008 01:59:49 -0000 On Mon, 9 Jun 2008, Bob McConnell wrote: > On Behalf Of cpghost >> On Sun, 8 Jun 2008 21:40:17 -0600 >> James wrote: >> >>> I have a high pitched whine coming from my motherboard when the EHCI >>> USB 2.0 controller is enabled in the BIOS. The whine only starts > once >>> FreeBSD 7.0-RELEASE is halfway through booting. >>> >>> The whine also goes away when I plugin a USB drive in with EHCI >>> controller enabled (usb keyboard and mouse being already plugged in). >>> >>> Is this a hardware problem, or could it possibly be software >>> related??? >> >> Hard to tell. I've had whining EPIA-boards when run at 1000 Hz, >> and after switching kern.hz to 100 Hz in /boot/loader.conf, the >> high-pitched whine stopped entirely. It also stopped when I >> slightly deviated from the 1000 Hz (to, say, 900 Hz or 1100 Hz), >> so there was obviously some hardware component on the boards >> oscillating like mad at this very frequency. >> >> I'm no specialist and it may be an urban legend, but from >> what I gathered, some coils could exhibit the behavior of >> generating those high-pitched whines when exposed to certain >> frequencies. >> >> -cpghost. > > No legends here. The horizontal sweep frequency for televisions in the > US is 17,500 Hz. It was 15,750 for original NTSC (black and white RS170), and changed to 15,734 when color (RS170A) came in in the 1950s. The vertical scan (field) rate also changed from 60 Hz to 59.94. These numbers were chosen because they are relatively easily derived from the newfangled color subcarrier of 3.579545 MHz, yet close enough to the old values that old pre-color TV sets could still lock to the new color signals. > Many people could hear that whistle from cheap flyback transformers. > Other devices would buzz, hum or rattle when they resonated with EM > fields. Occasionally they can be heard by humans, more frequently they > can be heard by their pets. As I have gotten older, I don't notice it > as much. The joke used to go, "Why did they pick that frequency?" "Well, the crusty old engineers just cranked it up until they couldn't hear the flyback anymore". I can still hear it, but then I'm still [just] on the candy-coated side of 50. I guess this is getting a little OT here... but by way of a half-assed response to the OP's question, I think Bob is on the right track - seems like an electromechanical resonance of some sort. -- Chris Hill chris@monochrome.org ** [ Busy Expunging <|> ]