From owner-freebsd-stable Tue Jul 20 23:28:16 1999 Delivered-To: freebsd-stable@freebsd.org Received: from zibbi.mikom.csir.co.za (zibbi.mikom.csir.co.za [146.64.24.58]) by hub.freebsd.org (Postfix) with ESMTP id EE11614E44 for ; Tue, 20 Jul 1999 23:27:58 -0700 (PDT) (envelope-from jhay@zibbi.mikom.csir.co.za) Received: (from jhay@localhost) by zibbi.mikom.csir.co.za (8.9.3/8.9.3) id IAA84801; Wed, 21 Jul 1999 08:27:13 +0200 (SAT) (envelope-from jhay) From: John Hay Message-Id: <199907210627.IAA84801@zibbi.mikom.csir.co.za> Subject: Re: Tuning the system's clock In-Reply-To: <000001bed2fc$593b6990$021d85d1@youwant.to> from David Schwartz at "Jul 20, 1999 03:08:08 pm" To: davids@webmaster.com (David Schwartz) Date: Wed, 21 Jul 1999 08:27:13 +0200 (SAT) Cc: stable@FreeBSD.ORG X-Mailer: ELM [version 2.4ME+ PL54 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-stable@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG > > FreeBSD's internal high-precision clock seems to be based on the > processor's instruction cycle counter. I've found that on one machine, the > clock is about 150 ppm fast. So I tried to reduce the machdep.tsc_freq > value. That was bad -- instant reboot. > > Is there a better way of adjusting that value? Changing 'tick' doesn't seem > to do much. I use it (machdep.tsc_freq and machdep.i8254_freq) here a lot and haven't seen any problems... except on machines like SMP boxes that don't use the tsc. There is does cause a panic. Bruce did fix it in current a few days ago, but I don't think it has filtered down to stable yet. > > Are the NTP pll values for mult/div documented anywhere? It seems to divide > before it multiplies, which means that using them for small offsets would > require high divisors, and hence a loss of accuracy. No it isn't documented anywhere AFAIK. Poul-Henning Kamp experimented with it a while back, but I'm not even sure he is using it anymore. It can probably be removed. John -- John Hay -- John.Hay@mikom.csir.co.za To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message