From owner-freebsd-questions@FreeBSD.ORG Thu May 5 09:20:12 2005 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 097EE16A4D2 for ; Thu, 5 May 2005 09:20:12 +0000 (GMT) Received: from mail.freebsd-corp-net-guide.com (mail.freebsd-corp-net-guide.com [65.75.192.90]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9983843D5E for ; Thu, 5 May 2005 09:20:11 +0000 (GMT) (envelope-from tedm@toybox.placo.com) Received: from tedwin2k (nat-rtr.freebsd-corp-net-guide.com [65.75.197.130]) j459Kdb61022 for ; Thu, 5 May 2005 02:20:39 -0700 (PDT) (envelope-from tedm@toybox.placo.com) From: "Ted Mittelstaedt" To: Date: Thu, 5 May 2005 02:20:08 -0700 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook IMO, Build 9.0.6604 (9.0.2911.0) X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1478 Importance: Normal In-Reply-To: <352039115.20050505104330@wanadoo.fr> Subject: RE: Clock running fast X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 05 May 2005 09:20:12 -0000 Anthony, you really need to look in the code sometime: /usr/src/sys/dev/acpica/acpi_timer.c * If all tests of the counter succeed, use the ACPI-fast method. If * at least one failed, default to using the safe routine, which reads * the timer multiple times to get a consistent value before returning. /usr/src/sys/i386/isa/clock.c the init routines for the i8254 clock chip /usr/src/sys/i386/i386/tsc.c { /* * We can not use the TSC if we support APM. Precise timekeeping * on an APM'ed machine is at best a fools pursuit, since * any and all of the time spent in various SMM code can't * be reliably accounted for. Reading the RTC is your only * source of reliable time info. The i8254 looses too of course * but we need to have some kind of time... * We don't know at this point whether APM is going to be used * or not, nor when it might be activated. Play it safe. */ Ted > -----Original Message----- > From: owner-freebsd-questions@freebsd.org > [mailto:owner-freebsd-questions@freebsd.org]On Behalf Of Anthony > Atkielski > Sent: Thursday, May 05, 2005 1:44 AM > To: freebsd-questions@freebsd.org > Subject: Re: Clock running fast > > > Charles Swiger writes: > > > Try changing the kern.timecounter.hardware sysctl; you can > look at the > > available choices via: > > > > sysctl kern.timecounter.choice > > So what do the choices mean? How are they used? > > On one machine, I see TSC, ACPI-fast, i8254, and dummy as choices, and > ACPI-fast is selected (this is a P4 machine). On the other, older > machine (a 2-processor Pentium Pro), I see TSC, i8254, and dummy, and > i8254 is selected. > > I presume that TSC is a real-time clock based on the processor TSC, and > I presume also that i8254 is such a clock based on the classic i8254 > timer, but what is dummy, and what is ACPI-fast? > > What are the pros and cons of selecting different choices? > > -- > Anthony > > > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to > "freebsd-questions-unsubscribe@freebsd.org" >