From owner-freebsd-current Sun Mar 26 20:48:53 1995 Return-Path: current-owner Received: (from majordom@localhost) by freefall.cdrom.com (8.6.10/8.6.6) id UAA03543 for current-outgoing; Sun, 26 Mar 1995 20:48:53 -0800 Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.34]) by freefall.cdrom.com (8.6.10/8.6.6) with ESMTP id UAA03537 for ; Sun, 26 Mar 1995 20:48:45 -0800 Received: (from bde@localhost) by godzilla.zeta.org.au (8.6.9/8.6.9) id OAA07627; Mon, 27 Mar 1995 14:44:42 +1000 Date: Mon, 27 Mar 1995 14:44:42 +1000 From: Bruce Evans Message-Id: <199503270444.OAA07627@godzilla.zeta.org.au> To: current@FreeBSD.org, starkhome!gene@sbstark.cs.sunysb.edu Subject: Re: Kernel time and xntpd Sender: current-owner@FreeBSD.org Precedence: bulk >I have been running xntpd for awhile now on some of my FreeBSD systems, >and it seems that xntpd has to perform a step adjustment of about >-0.14 sec approximately once an hour to stay in sync with a non-FreeBSD >remote time source. This is an error of about 40ppm. On the other hand, >other FreeBSD systems seem to stay in sync with a FreeBSD master with >a stability of less than 1ppm. This would seem to indicate that there >are still errors in the kernel timekeeping in FreeBSD. Are any currently >known? The 8254 timer frequency is very hardware dependent. I have two systems that have a relative drift of 3.6 seconds/hour. One drifts forwards, the other backwards. The frequency should be calibrated. This is easier if you have an accurate clock to calibrate it agains (the RTC is said to be less accurate and/or more unstable). Try changing TIMER_FREQ to ((int) (NOMINAL_TIMER_FREQ * (1 + 0.14 / 3600))). Bruce