From owner-freebsd-hackers Sun Mar 31 8:43:28 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from saruman.xwin.net (saruman.xwin.net [205.219.158.250]) by hub.freebsd.org (Postfix) with ESMTP id 0467237B416 for ; Sun, 31 Mar 2002 08:43:23 -0800 (PST) Received: from localhost (dp@localhost) by saruman.xwin.net (8.11.4/8.11.4) with ESMTP id g2VGit109003; Sun, 31 Mar 2002 10:44:55 -0600 Date: Sun, 31 Mar 2002 10:44:55 -0600 (CST) From: Paul Halliday X-X-Sender: dp@saruman.xwin.net To: Mike Silbersack Cc: Leo Bicknell , Subject: Re: GPS time. In-Reply-To: <20020331091304.U40871-100000@patrocles.silby.com> Message-ID: 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 Sun, 31 Mar 2002, Mike Silbersack wrote: > > 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. :) This is the answer I was kinda hoping for. I think that accuracy to ~100ms from a known source is a little more comforting than <1ms from a server that I have no control over. I am not maintaining a space program, just a dozen machines in my room that really serve no other purpose than personal entertainment. Thanks for all the replies! > > So, even at 100ms accuracy, it might be better to use a local GPS unit. > > > > Mike "Silby" Silbersack > > Paul H. "Don't underestimate the power of stupid people in large groups" ___________________ http://dp.penix.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message