[ntp:questions] Hopelessly broken clock?

Unruh unruh-spam at physics.ubc.ca
Sun Nov 16 17:47:44 UTC 2008

"Phil" <phil at xxxxxxxxx.xxx> writes:

>"Chris Richmond" <tomnykds at comcast.net> wrote in message 
>news:Xns9B57BC0965C12tomnykdscomcastnet at
>> 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

>May not be applicable in your case but I have multiple HP pc's and most were 
>running fast. I replaced batteries in all my machines that were a few years 
>old and it's amazing what a new battery will do.

You comment has to do with the on board Real Time Clock, not the system clock
which runs off the CPU/timer interrupt. He has trouble with the latter. 
It indicates problems with the clock calibration in his kernel. Or it could
have to do with "power saving" in which the CPU frequency is changed to
conserve power. As far as I know no operating system uses the RTC as the
timer, not least because it only has a 1 sec resolution.

>In my case we bought them on-line for about a buck each in quantity and I 
>changed batteries in all my electronics that used the 3-volt button 
>batteries. It may not get the local oscillator on the proper frequency, but 
>it should make it stable, a somewhat fixed drift rate. Just a thought.

It should be irrelevant to the system time, but not to the time set at


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