Slow Clock
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- Re: Slow Clock
Slow Clock
02-03-2010 12:47 PM
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The odd thing is that on the Laptop the clock slows down when running Xubuntu - I have just done this test:
I booted into the Xubuntu memory test option and that took about an hour. I then re-booted into the BIOS but the clock was still correct. However as soon as I actually ran Xubuntu the clock started losing time. After about an hour I re-booted again into the BIOS and the hardware clock was over 2 minutes slow! Obviously the OS uses the hardware clock as a reference when it starts up but then starts to alter it.
Left on it's own or running Vista the hardware clock keeps very good time.
Can anyone help?
dick:red All caps title fixed as per forum rules.
Re: Slow Clock
02-03-2010 4:36 PM
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Re: Slow Clock
02-03-2010 4:40 PM
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Re: Slow Clock
02-03-2010 4:48 PM
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It can do this - but Linux would normally compute an adjustment to your hardware clock and use this.
I believe it's possible to update your hardware clock periodically...
See http://tldp.org/HOWTO/Clock-2.html for a long description about time.
"In The Beginning Was The Word, And The Word Was Aardvark."
Re: Slow Clock
02-03-2010 5:02 PM
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Re: Slow Clock
02-03-2010 5:09 PM
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Quote from: custos Obviously the OS uses the hardware clock as a reference when it starts up but then starts to alter it.
The linux kernel itself doesn't affect the hardware clock. However some distributions do resynchronise the OS clock to the hardware clock at shutdown time, usually by running
hwclock --systohcin a shutdown script. It's feasible that this could be being run in cron to resynchronise on a regular basis so might be worth a check.
You can run (as root)
hwclock --showat any time to display the current hardware clock value and compare it to the OS clock value.
A quick Google shows that others have seen similar problems and that some motherboards are more prone. An example is http://ubuntuforums.org/showthread.php?t=75281.
Re: Slow Clock
02-03-2010 5:10 PM
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On Mint, choose Time & Date from the control panel and follow the same steps.
Re: Slow Clock
02-03-2010 7:20 PM
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Quote jeremy@HECTOR:~$ sudo hwclock --show
Tue 02 Mar 2010 19:12:21 GMT -0.859949 seconds
But I'm using ntpd to get the time off of the internet...
"In The Beginning Was The Word, And The Word Was Aardvark."
Re: Slow Clock
02-03-2010 8:34 PM
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Just to clarify:
The OS clock starts to run slowly immediately Xubuntu is running. The OS and hardware clocks do not stay synchronised but the OS clock loses approximately 2 minutes and 10 seconds every hour and the hardware clock is usually a little ahead but still slow. When I shut down Xubuntu the hardware clock stops losing time but is left at whatever time the OS clock was at exit. I can correct this using the BIOS or by running Vista, where I unusually use the time server update (manually) to get things back to normal.
I need the clock to be accurate to within a second or so and it normally is, so unless I can sort this out using Xubuntu is not going to be an option.
Re: Slow Clock
03-03-2010 1:15 AM
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In the package description its says:-
Quote NTP, the Network Time Protocol, is used to keep computer clocks
accurate by synchronizing them over the Internet or a local network,
or by following an accurate hardware receiver that interprets GPS,
DCF-77, NIST or similar time signals.
ntpdate is a simple NTP client that sets a system's clock to match
the time obtained by communicating with one or more NTP servers. It
is not sufficient, however, for maintaining an accurate clock in the
long run. ntpdate by itself is useful for occasionally setting the
time on machines that do not have full-time network access, such as
laptops.
If the full NTP daemon from the package "ntp" is installed, then
ntpdate is not necessary.
"In The Beginning Was The Word, And The Word Was Aardvark."
Re: Slow Clock
03-03-2010 9:43 AM
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Quote from: MrC The linux kernel itself doesn't affect the hardware clock.
That's not necessarily true. From the hwclock man page:
Quote You should be aware of another way that the Hardware Clock is kept synchronized in some systems. The Linux kernel has a mode wherein it copies the System Time to the Hardware Clock every 11 minutes
...
This mode (we'll call it "11 minute mode") is off until something turns it on. The ntp daemon xntpd is one thing that turns it on. You can turn it off by running anything, including hwclock --hctosys, that sets the System Time the old fashioned way.
To see if it is on or off, use the command adjtimex --print and look at the value of "status". If the "64" bit of this number (expressed in binary) equal to 0, 11 minute mode is on. Otherwise, it is off.
If your system runs with 11 minute mode on, don't use hwclock --adjust or hwclock --hctosys. You'll just make a mess.
Re: Slow Clock
03-03-2010 9:57 AM
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Re: Slow Clock
03-03-2010 11:03 AM
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I will leave it running while I take the dog for a walk and see how it is later.
jim:quote
Re: Slow Clock
03-03-2010 11:06 AM
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Re: Slow Clock
03-03-2010 12:04 PM
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Quote from: Hairy If it is still ok then you will need to follow the guide in post 17 (I think) to install it as default.
The clock was still correct after more than an hour. I have edited and saved grub and after a re-boot everything seems fine. I must try and work out what I have done now!
Thanks for your help.
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