Slashdot Mirror
Weird PC Clock Behavior?
cybercyst asks: "I've been having a problem with this for quite some time, and thought it was just me -- until two good friends of mine experienced the same problem. What we are experiencing is best described as a time-skew: our system time is apparently jumping forward an hour, and then returning to normal. It repeats this multiple times, and as far as I can tell only a reboot is any sort of remedy for this, albeit a temporary one. As you can imagine this causes all sorts of problems (under windows managers xscreensaver is always popping up -- in fact as I wrote this, the screensaver has come on over 10 times, negative fps in OpenGL programs, extremely large ping times, and so forth)."
"Friend A runs an Athlon system on a Soyo Dragon motherboard, I'm running a K6-2 450Mhz CPU on an older Epox motherboard. We are both running Slackware 8.0 with kernel 2.4.17, but Friend B runs nothing but Red Hat, and kernel 2.4.2-2.
I have personally tried many things to get this fixed permanently, including setting the time with 'date -s; hwclock --hctosys; hwclock --systohc' the BIOS is set to the right time that doesn't seems to help! So, I'm asking Slashdot, Has anyone out there encountered a similar problem, and if they have, have you been able to fix it?"
Nothing beats your very own nuclear clock on a PCI card. The best they can make you is a rubidium standard clock accurate to 10^-13 seconds. Cesium beam clocks accurate to 10^-17 seconds are available in rackmount form. Great for all those Mission Critical Real Time applications like Quake III.
If voting were effective, it would be illegal by now.
You might have to delete /etc/adjtime after adjusting your clock. This file is updated now and then to prevent clock drift.
'man 8 hwclock' and 'The Adjust Function' might give you some answers.
Give it a shot, at least.
Jakob Breivik Grimstveit
"I love deadlines. I love the whooshing noise they make as they go by."
Goodtimes is cross-platform.
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Oregon
I know where you are coming from! This time shift has been a major headache for me at work. My group installs computer systems at emergency management agencies (EMAs) that selectively trigger radios by a precoded geographical zone or serial number. We have a security feature in our broadcast that is basically a time stamp - the radio rejects a broadcast if the timestamp is more than 5 minutes off its internal clock. This prevents somebody from taping a monthly test message and rebroadcasting it at three in the morning to falsely trigger the radios. Well, at the EMAs they just want to sit down at the PC during an emergency and click on a button - so the PC is ignored until it's really needed and then they don't want to waste time checking to see if the clock has jumped. If it has, oops, the broadcast timestamp doesn't match and the radios don't trigger!!!
We have never figured out how to stop the computer time from jumping and if anyone else has, please let me know! The workaround solution we've come up with is to either install a network time update program running in the background if the computer is on the web (for examples, search for "time sync" hereor for the more common rural EMAs that have no Internet connection, we install clock boards. We have found three sources for clock boards: Beagle Software, OutSource and ICS Advent. The Beagle product is ISA only, the OutSource product only works with Win 2000/NT (not Win 95/98) and the ICS product is far and away the most expensive. If anybody knows of others besides these three, please let me know!
You want to be sure that you only have one time synchronization daemon running. It sounds like you might have more than one, with one misconfigured to ignore daylight savings time or something similar.
ntp is the most robust free time synchronization software. Try using that in preference to rdate, timed, timeslave, etc. Test ntpd by using "ntpdate" against your upstream ntpd time servers to make sure they do what you expect.
UTC=false
Because Windows diddles with the hardware clock directly, it can't be used (directly) as a UTC time source for UNIX.
Naturally, if you're ONLY running Linux, you can have UTC=true and forget about it.
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This is just a guess, but could your problems be related to apm or some other power management features? A bit over a year ago I was playing with apm on my Linux desktop. Whenever the computer went into a suspend or low-power mode, my clock would be completely messed up by several hours. I'm not sure if it was a bug on my motherboard, a bug in the apm code, or just that I'd misconfigured something. Either way, I just disabled all power management features (except using xset to turn off the monitor with dpms) and haven't had a problem since.
If you try this, you'll probably want to turn power management off both in software (remove apmd etc.) and in the motherboard's bios settings. Most motherboards should allow you to do this.
Good luck!
It's only software!
Trimble makes a product called Accutime 2000 http://www.trimble.com/acutime2000.html That can basically plug right into the ether.
Hokey name, but I'm told it works pretty good. The local telco (MTS) uses one for it's time source.
Cheers!
John
The only time I've ever witnessed something like this was when I serviced a client who kept complaining about time jumps (usually backwards and in large hour chunks). I'd swapped all the hardware several times (motherboard, battery, processor, memory, all the ISA cards, etc).
Finally, I saw it happen. It was right about lunch time and on the other side of the wall was the worlds oldest radar range (pre Microwave Oven). That sucka kicked in when someone heated their lunch and the clock on the computer actually ran backwards!
I had to move the desk away from the wall several feet and the problem stopped happening.
More than likely though, the problem is with a buggy BIOS or dying battery. Replace the battery, flash your BIOS to the latest revision. If this doesn't work then you're only out about $10.00. Next step is to either buy an add-on time device that works properly or if you have a net connection running all the time, look into the NTP (Network Time Protocols) to sync with the Naval Observatory or another good source for correct time on as frequently a basis as you require.
Also check out the Linux clock features like the realtime daemon, it's not for realtime as in realtime OS but for more accurate time keeping. Red Hat has this daemon by default.
Check your security, make sure a co-worker is not just trying to mess with your head by changing your clock remotely.