[ntp:questions] Hopelessly broken clock?

Juergen Perlinger juergen.perlinger at t-online.de
Sat Dec 27 19:53:34 UTC 2008


Chris Richmond wrote:

> I'm trying to set up ntp on a new Core2 Duo box running Fredora Core9.
> It appears that it's local clock runs several seconds an hour fast.  I'm
> basing this on running ntpdate against the existing box I have running
> ntp with pps.  It reports skewing the clock by seconds even after just
> a few minutes.
> 
> Also, ntpq data shows the jitter as always 0.997, and the offset goes
> nuts right away.  The poll and reach look like they are working, but
> the time just gets away really fast.
> 
> I have another box with the same O/S install and ntp config, and it locks
> up right away just fine, so I suspect it's a hardware issue, not a
> config problem.
> 
> I've tried to read through the offical docs on the NTP web site on
> diagnosing problems, but can't make sense of what some of the
> instructions mean. What's missing are examples of what actually
> needs to happen.
> 
> In any case, if the actual box's clock is that far off, is it a lost
> cause as a time keeper?
> 
> Can I make ntptime correct the kernel's clock enough to get this
> to work?  If so, how, and can this be done in the bootup scripts?
> 
> Thx, Chris

I have a deja vu... again.

See the support twiki for some hints about linux, but I had similar trouble.
Try to configure your kernel with a 'clocksource=acpi_pm'
or 'clocksource=hpet' and see what happens. A lot of systems try to use the
TSC as clocksource, and the TSC frequency is not constant but varies due to
power management actions.

Have a look at the twiki
at 'https://support.ntp.org/bin/view/Support/KnownOsIssues#Section_9.2.4.2.8.'
-- 
juergen 'pearly' perlinger
"It's hard to make new errors!"




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