From owner-freebsd-hackers Sun Mar 31 1:17:48 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from patrocles.silby.com (d177.as7.nwbl0.wi.voyager.net [169.207.130.115]) by hub.freebsd.org (Postfix) with ESMTP id 38EA437B405 for ; Sun, 31 Mar 2002 01:17:44 -0800 (PST) Received: from patrocles.silby.com (localhost [127.0.0.1]) by patrocles.silby.com (8.12.2/8.12.2) with ESMTP id g2VFGQUH040894; Sun, 31 Mar 2002 09:16:26 -0600 (CST) (envelope-from silby@silby.com) Received: from localhost (silby@localhost) by patrocles.silby.com (8.12.2/8.12.2/Submit) with ESMTP id g2VFGNOX040891; Sun, 31 Mar 2002 09:16:25 -0600 (CST) X-Authentication-Warning: patrocles.silby.com: silby owned process doing -bs Date: Sun, 31 Mar 2002 09:16:18 -0600 (CST) From: Mike Silbersack To: Leo Bicknell Cc: Paul Halliday , Subject: Re: GPS time. In-Reply-To: <20020330142859.GA19243@ussenterprise.ufp.org> Message-ID: <20020331091304.U40871-100000@patrocles.silby.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Sat, 30 Mar 2002, Leo Bicknell wrote: > Your NTP servers are better. > > I tested a III Plus, and without a 1 PPS source (which that model > doesn't provide) it's accurate to about 100ms, give or take. Since > real NTP servers are < 1ms, they really aren't that good. It's > not that the time isn't accurate, it's that they were not designed > to communicate with that accuracy to an external device. OTOH, 100ms is pretty close; I doubt many people need time better than that. The one big advantage I can see with using a GPS receiver vs NTP servers is security & reliability; I've always worried that my clock might start to drift to a misconfigured NTP server. Taken to a paranoid level, you could worry that someone was faking NTP replies to throw your clocks off. :) So, even at 100ms accuracy, it might be better to use a local GPS unit. Mike "Silby" Silbersack To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message