From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936707AbXG0L5W (ORCPT ); Fri, 27 Jul 2007 07:57:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1763562AbXG0L5N (ORCPT ); Fri, 27 Jul 2007 07:57:13 -0400 Received: from smtp4-g19.free.fr ([212.27.42.30]:51791 "EHLO smtp4-g19.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759268AbXG0L5M (ORCPT ); Fri, 27 Jul 2007 07:57:12 -0400 Message-ID: <46A9DD7A.80104@free.fr> Date: Fri, 27 Jul 2007 13:56:42 +0200 From: John Sigler User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061108 SeaMonkey/1.0.6 MIME-Version: 1.0 To: linux-kernel@vger.kernel.org, linux-rt-users Subject: System clock frequency offset changes drastically across reboots Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hello everyone, I'm using 2.6.20.7-rt8 on a P3. I've noticed that the frequency offset of my system clock (computed either by ntpd, or by hand) changes drastically across reboots. By drastically, I mean +/- 60 ppm every time I reboot. Apparently this is caused by some imprecision in the frequency estimation done in calculate_cpu_khz() (arch/i386/kernel/tsc.c) My brutally crude work-around was to skip the computation altogether and hard-code the "correct" value for cpu_khz. http://linux.kernel.free.fr/cpu_khz.adlink Has this issue been investigated more thoroughly by other users? Regards.