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Author Topic: hwclock drift  (Read 1607 times)
suncream25
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« on: April 18, 2010, 06:29:12 AM »


I'm currently using the following commands to set the plug clock date & time:

# dpkg-reconfigure tzdata
# ntpdate-debian
# /sbin/hwclock –systohc

I am noticing a drift in the plug clock time once the plug has been disconnected from the network. Any thoughts?



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fragfutter
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« Reply #1 on: April 18, 2010, 07:29:32 AM »

why are you reconfiguring the timezone every time? Once should be enough Wink

ntpdate-debian will set the time once. I have no idea how good the internal clock is, but for a better timekeeping you might want to run ntpd. It will continuously adjust the time. It also keeps a drift file, that has the average drift of the internal clock. If the internal clock isn't flactuating too much, this should (after a while) provide a good enough correction even without network.
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MarkF
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« Reply #2 on: April 22, 2010, 12:27:31 PM »

As fragfutter said, using ntpd with recent kernels offers the capability of dramatically reducing, but not eliminating, running clock drift.  One caveat: you need to run the plug for about 15 minutes with it hooked to a network with an available ntp server (the internet) for the ntpd algorithms to have enough difference data to do proper drift analysis.

FYI, no matter how good the drift analysis is, the longer the plug is not connected to a ntp server or stratum-0 device (atomic clock, GPS, radio clock, etc), the more drift it will have.  This is true whether the plug is running or not.
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Mark

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