From owner-freebsd-stable@FreeBSD.ORG Fri May 11 18:53:56 2007 Return-Path: X-Original-To: freebsd-stable@FreeBSD.ORG Delivered-To: freebsd-stable@FreeBSD.ORG Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id BFFDF16A400 for ; Fri, 11 May 2007 18:53:56 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from harmony.bsdimp.com (vc4-2-0-87.dsl.netrack.net [199.45.160.85]) by mx1.freebsd.org (Postfix) with ESMTP id 7B3A213C448 for ; Fri, 11 May 2007 18:53:56 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from localhost (localhost [127.0.0.1]) by harmony.bsdimp.com (8.13.8/8.13.4) with ESMTP id l4BIpqu7090950; Fri, 11 May 2007 12:51:53 -0600 (MDT) (envelope-from imp@bsdimp.com) Date: Fri, 11 May 2007 12:51:55 -0600 (MDT) Message-Id: <20070511.125155.1021575722.imp@bsdimp.com> To: tevans.uk@googlemail.com From: "M. Warner Losh" In-Reply-To: <1178900585.1231.63.camel@zoot.mintel.co.uk> References: <20070511110759.L700@thinkpad.dieringer.dyndns.org> <20070511.085325.-1889956816.imp@bsdimp.com> <1178900585.1231.63.camel@zoot.mintel.co.uk> X-Mailer: Mew version 4.2 on Emacs 21.3 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.0 (harmony.bsdimp.com [127.0.0.1]); Fri, 11 May 2007 12:51:53 -0600 (MDT) Cc: freebsd-stable@FreeBSD.ORG, martin.dieringer@gmx.de Subject: Re: clock problem X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 11 May 2007 18:53:56 -0000 In message: <1178900585.1231.63.camel@zoot.mintel.co.uk> Tom Evans writes: : On Fri, 2007-05-11 at 08:53 -0600, M. Warner Losh wrote: : > In message: <20070511110759.L700@thinkpad.dieringer.dyndns.org> : > Martin Dieringer writes: : > : This is NOT a hardware problem. 1. I have this on 2 machines, 2. the : > : problem is solved by switching to ACPI instead of APM : > : > It is a hardware problem. APM + powerd changes the frequency of the : > TSC. If the TSC is used as the time source, then you'll get bad : > timekeeping. ACPI uses its own frequency source that is much more : > stable and independent of the TSC, so switching to it fixes the : > problem because you are switching the hardware from using a really bad : > frequency source with ugly steps to using a good frequency source w/o : > steps. : > : > Warner : : Surely that would imply that it is a software misconfiguration issue. If : the TSC is unreliable under fairly standard duties, and there exists an : alternate source that is reliable, surely that indicates the : manufacturer has identified a problem, and solved it with alternate : hardware. : : The failure then to use the correct hardware is a software : misconfiguration. TSC is very accurate if you don't have the clock frequency slammed around, which is why its quality is listed as 800 and the i8254 is listed as 0. If you do anything that slams the TSC frequency, then you need to reconfigure the timecounter used. It is hard for the timekeeping part of the software to know if you are on a sane system (TSC-wise) or an insane one. Warner