From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 5 May 2002 21:37:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 5 May 2002 21:37:35 -0400 Received: from c9mailgw02.amadis.com ([216.163.188.207]:15876 "EHLO C9Mailgw02.amadis.com") by vger.kernel.org with ESMTP id ; Sun, 5 May 2002 21:37:34 -0400 Message-ID: <3CD5DE56.B8A4C74D@starband.net> Date: Sun, 05 May 2002 21:37:26 -0400 From: Justin Piszcz X-Mailer: Mozilla 4.79 [en] (X11; U; Linux 2.4.18 i686) X-Accept-Language: en MIME-Version: 1.0 To: "David D. Hagood" CC: linux-kernel@vger.kernel.org Subject: Re: Linux & X11 & IRQ Interrupts In-Reply-To: <3CD5D57D.DED89DFC@starband.net> <3CD5DD6D.60800@sktc.net> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Ahh... Thanks for the information. "David D. Hagood" wrote: > Justin Piszcz wrote: > > > With the console speaker attached, it can be clearly heard, as well as > > performing fast packet movements (nmap (with insane option)) or such you > > can literally hear the packets. > > What you are hearing is the noise in the computer's power supply. As the > load on the power supply changes, the voltage changes by a few tens of > millivolts, and that is the noise you are hearing. > > This primary reason you don't hear this under Windows and you hear it > under Linux is that Linux will shut the processor off when there is > nothing to do, greatly reducing the load on the power supply. When > something happens, like a mouse interrupt or a network interrupt, the > CPU springs back to life, drawing a burst of power from the power supply > and momentarily bringing the voltage down a bit. This cycling of the CPU > happens in microseconds. > > Windows, especially older versions of Windows, doesn't do this - when > there is no work for the CPU, it spins in a busy loop looking for work. > As a result, the load on the power supply never changes. Of course, your > system will also run hotter and burn more power. > > If this bothers you, you could try getting another power supply (one > that is "stiffer" and less prone to voltage sag) or you could run a > program like Seti@home or Distributed.Net and keep your CPU busy all the > time.