Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756119AbXICKWY (ORCPT ); Mon, 3 Sep 2007 06:22:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752717AbXICKWP (ORCPT ); Mon, 3 Sep 2007 06:22:15 -0400 Received: from smtp4-g19.free.fr ([212.27.42.30]:44458 "EHLO smtp4-g19.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752330AbXICKWN (ORCPT ); Mon, 3 Sep 2007 06:22:13 -0400 Message-ID: <46DBE031.1090808@free.fr> Date: Mon, 03 Sep 2007 12:21:37 +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 CC: johnstul@us.ibm.com, tglx@linutronix.de 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 Content-Length: 971 Lines: 29 [ Re-sending... Please feel free to comment, even if you don't have "The Solution". I'd just like to get some feedback. ] 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. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/