Date: Thu, 16 Dec 1999 13:41:53 -0700 From: Warner Losh <imp@village.org> To: nate@mt.sri.com (Nate Williams) Cc: "FreeBSD Current Users' list" <freebsd-current@FreeBSD.ORG> Subject: Re: HEADSUP: ntp4 to replace xntpd Message-ID: <199912162041.NAA73896@harmony.village.org> In-Reply-To: Your message of "Thu, 16 Dec 1999 13:35:23 MST." <199912162035.NAA20788@mt.sri.com> References: <199912162035.NAA20788@mt.sri.com> <199912161810.LAA19919@mt.sri.com> <Pine.BSF.4.05.9912160934230.23583-100000@semuta.feral.com> <16818.945366687@critter.freebsd.dk> <199912162032.NAA73759@harmony.village.org>
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In message <199912162035.NAA20788@mt.sri.com> Nate Williams writes: : > : You may not know the answer to this, but it's worth a shot. Wht kind of : > : accuracy can we expect using 'cheap' off-the-shelf GPS receivers? : > : > We're getting, with ntp4 on a 3.x kernel, about +- 4uSec with a cheap : > gps receiver + atomic clock on a i486 class machine. : : I've got the cheap gps receiver (Garmin 12XL), but what do you mean by : an 'atomic clock'? Should the GPS receiver's NMEA messages be adequate : enough to do the job? However, all I need is ms accuracy, so anything : below 500us is good enough for me. We have a cesium clock, which is generally called atomic clock, that we use for various things in our system. If the GPS gives out a PPS signal for the NMEA, then you can likely hit 1mS w/o any problems at all. Don't know a thing about the Garmin 12XL to know for sure about how it operates. Warner To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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