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From: thorinn@DIKU.DK (Lars Henrik Mathiesen)
Newsgroups: comp.archives
Subject: [ntp] NTP and the infamous SPARC clock problem (again)
Message-ID: <1990Dec3.031806.23057@ox.com>
Date: 3 Dec 90 03:18:06 GMT
References: <9011300932.aa09771@Obelix.TWG.COM> <9012021546.AA28726@rimfaxe.diku.dk>
Sender: emv@ox.com (Edward Vielmetti)
Reply-To: thorinn@DIKU.DK (Lars Henrik Mathiesen)
Followup-To: comp.protocols.time.ntp
Organization: The Internet
Lines: 34
Approved: emv@ox.com (Edward Vielmetti)
X-Original-Newsgroups: comp.protocols.time.ntp

Archive-name: internet/ntp/ntp-timed-patch/1990-12-02
Archive: freja.diku.dk:misc/ntp-timed.patch [129.142.96.1]
Original-posting-by: thorinn@DIKU.DK (Lars Henrik Mathiesen)
Original-subject: NTP and the infamous SPARC clock problem (again)
Reposted-by: emv@ox.com (Edward Vielmetti)

Edward,

We run a flock of VAXen on ntp, and on those we run a jimmied timed
whose only function is to act as master for our various Suns (*).
This works fine now that we've set dosynctodr to 0 in the Sun
kernels; I just checked, and most Suns are within 25 ms of the
current timed master. The SparcStations all run very fast and will
gain about 75 ms between timed syncs (every four minutes); but as
someone suggested, we could set tick to 9998 which would probably
bring them into line.

(Before we reset dosynctodr, we'd see the SparcStation clocks slew up
to sync once every four minutes and then slew even faster (about 1
second in two!) back to an (increasing) offset of up to 20 seconds.
When the offset grew larger than that, timed would log a complaint and
do a settimeofday, starting the cycle again.)

It seems that an unloaded SparcStation with dosynctodr==0 is about 300
ppm fast (about 30 seconds a day). When it was set, they'd generate a
timed log message every three to four hours during working hours only
(about 1500 ppm slow). I guess the slowness when loaded is due to lost
clock interrupts although I'm unable to imagine what sort of bogosity
in SunOS is is that makes this time loss persistent when using the
time-of-day register.

Lars
_____________________________________________________________________
(*) Patches for anonymous ftp at freja.diku.dk:misc/ntp-timed.patch .


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