Date: Wed, 22 Aug 2001 22:49:06 -0600 From: Warner Losh <imp@harmony.village.org> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: Thierry Herbelot <thierry@herbelot.com>, hackers@FreeBSD.ORG Subject: Re: clock synchronization quality via NTP ? Message-ID: <200108230449.f7N4n6W81268@harmony.village.org> In-Reply-To: Your message of "Thu, 23 Aug 2001 06:43:26 %2B0200." <46651.998541806@critter> References: <46651.998541806@critter>
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In message <46651.998541806@critter> Poul-Henning Kamp writes: : In message <200108230242.f7N2gfW80510@harmony.village.org>, Warner Losh writes: : : >: More precisely : is it reasonable to hope having a system clock not : >: farther from the GPS clock by more than 50 micro-seconds ? : : 50 microseconds should be feasible provided that you either : provide a very stable temperature or replace the 14.318 MHz : xtal on the motherboard with a something more stable. Yea. I just took a look at the data that we have, and we're seeing more like +- 15us on machines here without temerpature stability beyond "normal HVAC" and stock xtals on the motherboard. This is after we've done the fast interrupt hack. Without it, the other system activity was causing enough interrupt latncy variance that we would see more like +- 80us with outliers way off in the weeds (+- just under 10ms!). Warner To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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