Re: [ntp:questions] Using two NTP Server: Bad?
>> Consider that "failure" here encompasses "serves bogus time". Suppose >> you have 7 sources configured and 4 of them cluster nicely around an >> incorrect time, with 3 clustered around UTC. >I suppose it's possible but I'm not going to hold my breath waiting for >an instance to appear! All it takes is a firmware bug and to have several NTP servers using the same GPS device with the bug. -- These are my opinions, not necessarily my employer's. I hate spam. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Using two NTP Server: Bad?
On 2011-04-23, Hal Murray wrote: >>> Consider that "failure" here encompasses "serves bogus time". Suppose >>> you have 7 sources configured and 4 of them cluster nicely around an >>> incorrect time, with 3 clustered around UTC. > >>I suppose it's possible but I'm not going to hold my breath waiting for >>an instance to appear! > > All it takes is a firmware bug and to have several NTP servers > using the same GPS device with the bug. What good will having more servers do then? If the probablility of 4 bad ones is that high, the probability of 5 out of 9 is also high, and 6 out of 11. Ie, in that case you are basically screwed. Of course everyone could just use the national time standards servers-- they are not liable to be wrong (maybe just overloaded). > > ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
On 2011-04-23, David J Taylor wrote: > "Richard B. Gilbert" wrote in message > news:ot-dnvdagogjoizqnz2dnuvz_o-dn...@giganews.com... > [] >> Anyone who doubts the accuracy, legitimacy, etc. of pool services should >> be able to purchase a GPS timing receiver and get the time from "the >> horse's mouth". The investment required is about $100 US at a minimum. > > Even less - US $34 now He did say a "timing receiver". That could mean a GPS receiver specifically set up to supply time, including an on board temp insensitive crystal to supply the time if the sattelite availability goes to low. Also it is $42 since you need to receive it, unless you happen to be visiting Hong Kong. And then you have to solder a few wires onto surface mount pins. > > http://www.sureelectronics.net/goods.php?id=99 > http://www.satsignal.eu/ntp/Sure-GPS.htm > > Cheers, > David > ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
"unruh" wrote in message news:slrnir4tou.j3t.un...@wormhole.physics.ubc.ca... [] He did say a "timing receiver". That could mean a GPS receiver specifically set up to supply time, including an on board temp insensitive crystal to supply the time if the sattelite availability goes to low. .. and I don't think that the US $100 GPS 18x LVC claims to have that. Also it is $42 since you need to receive it, unless you happen to be visiting Hong Kong. And then you have to solder a few wires onto surface mount pins. .. but you don't need to pay US $100. Oh, and you do need to solder with the GPS 18X LVC as well. Personally, I am delighted with the choice of GPS/PPS receivers now available at very affordable prices, and welcome the choice. "You pays your money and takes your choice". Cheers, David ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
David J Taylor wrote: > "unruh" wrote in message > news:slrnir4tou.j3t.un...@wormhole.physics.ubc.ca... > [] >> He did say a "timing receiver". That could mean a GPS receiver >> specifically set up to supply time, including an on board temp >> insensitive crystal to supply the time if the sattelite availability >> goes to low. > > .. and I don't think that the US $100 GPS 18x LVC claims to have that. > >> Also it is $42 since you need to receive it, unless you happen to be >> visiting Hong Kong. >> And then you have to solder a few wires onto surface mount pins. > > .. but you don't need to pay US $100. Oh, and you do need to solder with > the GPS 18X LVC as well. > > Personally, I am delighted with the choice of GPS/PPS receivers now > available at very affordable prices, and welcome the choice. "You pays > your money and takes your choice". Why is this irrelevant discussion started every time some topic is being discyssed in this newsgroup? It does not matter what the initial question is, what problem someone tries to solve, what requirements he has, what limitations he may have, what possibilities there are in solving the issue at hand, there is always someone who brings up the #$%^@$@ GPS receiver and starts boasting the price it may be acquired for. Please people, please grow up. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
David J Taylor wrote: > "Rob" wrote in message > news:slrnir54hp.hnj.nom...@xs8.xs4all.nl... > [] >> The initial question: >> | Due to my wandering use of a laptop for, "work" (cough!) Often away >> | from the office, and our server, but with local internet access (Hotel >> | WiFi etc). >> | >> | What UK based "RELIABLE" (cant emphasize that enough) UK time >> server(s) >> | would the group recomend I point Windows time sync' to? >> >> and the subsequent discussion about the NTP pool and its reliability, >> and how many servers from the pool one would resonably use to get good >> results without overloading a voluntarily provided service, is a good >> and valid discussion on its own. >> >> There is no need to pollute that discussion by talking about GPS >> receivers >> yet again. It is not a solution for the original poster, and it does >> not contribute to the discussion about either of the topics brought up. >> >> You may be exited about your new GPS receiver toy, but there is no need >> to recommend that hammer as the only tool one will ever need. It isn't. > > .. and why shouldn't someone consider taking a GPS 18x LVC as a portable > time reference? He is asking for reliable UK-based time servers to use in a hotel room via the provided internet access. Not for a GPS receiver. > BTW: I did not start the GPS discussion. The discussion is running here so often that it is getting difficult to find who is starting it. But it is not the hammer that can be used as the universal tool unless you believe that everything is a nail. (which some people here seem to believe) ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
"Rob" wrote in message news:slrnir52mv.hnj.nom...@xs8.xs4all.nl... [] Why is this irrelevant discussion started every time some topic is being discyssed in this newsgroup? It does not matter what the initial question is, what problem someone tries to solve, what requirements he has, what limitations he may have, what possibilities there are in solving the issue at hand, there is always someone who brings up the #$%^@$@ GPS receiver and starts boasting the price it may be acquired for. Please people, please grow up. Rob, GPS/PPS is, perhaps, the most used reference source for stratum-1 clocks with NTP, so they are hardly "irrelevant", and for the OP who wants reliable time when away from the office, a portable GPS receiver may be a candidate solution. For many folk, those paying out of their own pockets, the cost matters. Having said that, I have already made my suggestion to the OP based on what I do myself - to use NTP and the pool servers. Cheers, David ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
"Rob" wrote in message news:slrnir54hp.hnj.nom...@xs8.xs4all.nl... [] The initial question: | Due to my wandering use of a laptop for, "work" (cough!) Often away | from the office, and our server, but with local internet access (Hotel | WiFi etc). | | What UK based "RELIABLE" (cant emphasize that enough) UK time server(s) | would the group recomend I point Windows time sync' to? and the subsequent discussion about the NTP pool and its reliability, and how many servers from the pool one would resonably use to get good results without overloading a voluntarily provided service, is a good and valid discussion on its own. There is no need to pollute that discussion by talking about GPS receivers yet again. It is not a solution for the original poster, and it does not contribute to the discussion about either of the topics brought up. You may be exited about your new GPS receiver toy, but there is no need to recommend that hammer as the only tool one will ever need. It isn't. .. and why shouldn't someone consider taking a GPS 18x LVC as a portable time reference? BTW: I did not start the GPS discussion. David ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
David J Taylor wrote: > "Rob" wrote in message > news:slrnir52mv.hnj.nom...@xs8.xs4all.nl... > [] >> Why is this irrelevant discussion started every time some topic is >> being discyssed in this newsgroup? >> It does not matter what the initial question is, what problem someone >> tries to solve, what requirements he has, what limitations he may have, >> what possibilities there are in solving the issue at hand, there is >> always someone who brings up the #$%^@$@ GPS receiver and starts >> boasting >> the price it may be acquired for. >> >> Please people, please grow up. > > Rob, > > GPS/PPS is, perhaps, the most used reference source for stratum-1 clocks > with NTP, so they are hardly "irrelevant", and for the OP who wants > reliable time when away from the office, a portable GPS receiver may be a > candidate solution. For many folk, those paying out of their own pockets, > the cost matters. > > Having said that, I have already made my suggestion to the OP based on > what I do myself - to use NTP and the pool servers. The initial question: | Due to my wandering use of a laptop for, "work" (cough!) Often away | from the office, and our server, but with local internet access (Hotel | WiFi etc). | | What UK based "RELIABLE" (cant emphasize that enough) UK time server(s) | would the group recomend I point Windows time sync' to? and the subsequent discussion about the NTP pool and its reliability, and how many servers from the pool one would resonably use to get good results without overloading a voluntarily provided service, is a good and valid discussion on its own. There is no need to pollute that discussion by talking about GPS receivers yet again. It is not a solution for the original poster, and it does not contribute to the discussion about either of the topics brought up. You may be exited about your new GPS receiver toy, but there is no need to recommend that hammer as the only tool one will ever need. It isn't. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
On 4/23/2011 4:16 AM, Rob wrote: David J Taylor wrote: "unruh" wrote in message news:slrnir4tou.j3t.un...@wormhole.physics.ubc.ca... [] He did say a "timing receiver". That could mean a GPS receiver specifically set up to supply time, including an on board temp insensitive crystal to supply the time if the sattelite availability goes to low. .. and I don't think that the US $100 GPS 18x LVC claims to have that. Also it is $42 since you need to receive it, unless you happen to be visiting Hong Kong. And then you have to solder a few wires onto surface mount pins. .. but you don't need to pay US $100. Oh, and you do need to solder with the GPS 18X LVC as well. Personally, I am delighted with the choice of GPS/PPS receivers now available at very affordable prices, and welcome the choice. "You pays your money and takes your choice". Why is this irrelevant discussion started every time some topic is being discyssed in this newsgroup? It does not matter what the initial question is, what problem someone tries to solve, what requirements he has, what limitations he may have, what possibilities there are in solving the issue at hand, there is always someone who brings up the #$%^@$@ GPS receiver and starts boasting the price it may be acquired for. Please people, please grow up. Physician, heal thy self! ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
On 4/23/2011 2:52 AM, unruh wrote: On 2011-04-23, David J Taylor wrote: "Richard B. Gilbert" wrote in message news:ot-dnvdagogjoizqnz2dnuvz_o-dn...@giganews.com... [] Anyone who doubts the accuracy, legitimacy, etc. of pool services should be able to purchase a GPS timing receiver and get the time from "the horse's mouth". The investment required is about $100 US at a minimum. Even less - US $34 now He did say a "timing receiver". That could mean a GPS receiver specifically set up to supply time, including an on board temp insensitive crystal to supply the time if the sattelite availability goes to low. There is no such thing as a "temp insensitive crystal"! A crystal can be placed in a tiny temperature controlled oven to achieve the *effect* of temperature insensitivity. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
[ntp:questions] Bug 1700 - Clock drifts excessively at polling levels above 256.
Edward T. Mischanko | Maintenance Technician, Electrical ArcelorMittal Burns Harbor Finishing | 250 W. US Highway 12 Burns Harbor, IN 46304-9745 T +1 219 787 3601 | F +1 219 787 4510 www.arcelormittal.com _ From: Mischanko, Edward T Sent: Thursday, April 21, 2011 12:02 PM To: 'questions@lists.ntp.org' Subject: Bug 1700 - Clock drifts excessively at polling levels above 256. My system clock drifts excessively when polling above 256 in a Windows environment, as much as 5 ms or more. I have made changes to .../ntpd/ntp_loopfilter.c CLOCK_PLL, CLOCK_FLL, CLOCK_LIMIT, and CLOCK_PGATE to address this problem. I realize the changes I have made are global in nature and really only need changes in the Windows port. I would welcome a patch to the Windows port to accomplish these changes or any other changes that accomplish the 1 ms stability I have now achieved. I hope Dr. Mills will have constructive comments on this problem and proposed solutions. /* * This is an implementation of the clock discipline algorithm described * in UDel TR 97-4-3, as amended. It operates as an adaptive parameter, * hybrid phase/frequency-lock loop. A number of sanity checks are * included to protect against timewarps, timespikes and general mayhem. * All units are in s and s/s, unless noted otherwise. */ #define CLOCK_MAX .128 /* default step threshold (s) */ #define CLOCK_MINSTEP 300./* default stepout threshold (s) */ #define CLOCK_PANIC 1000. /* default panic threshold (s) */ #define CLOCK_PHI 15e-6 /* max frequency error (s/s) */ #define CLOCK_PLL 1.8 /* PLL loop gain (log2) */ #define CLOCK_AVG 8. /* parameter averaging constant */ #define CLOCK_FLL .001 /* FLL loop gain */ #define CLOCK_FLOOR .0005 /* startup offset floor (s) */ #define CLOCK_ALLAN 11 /* Allan intercept (log2 s) */ #define CLOCK_DAY 86400. /* one day in seconds (s) */ #define CLOCK_JUNE (CLOCK_DAY * 30)/* June in seconds (s) */ #define CLOCK_LIMIT 15 /* poll-adjust threshold */ #define CLOCK_PGATE 2. /* poll-adjust gate */ #define PPS_MAXAGE 120 /* kernel pps signal timeout (s) */ #define FREQTOD(x) ((x) / 65536e6) /* NTP to double */ #define DTOFREQ(x) ((int32)((x) * 65536e6))/* double to NTP */ ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
Richard B. Gilbert wrote: On 4/23/2011 2:52 AM, unruh wrote: On 2011-04-23, David J Taylor wrote: "Richard B. Gilbert" wrote in message news:ot-dnvdagogjoizqnz2dnuvz_o-dn...@giganews.com... [] Anyone who doubts the accuracy, legitimacy, etc. of pool services should be able to purchase a GPS timing receiver and get the time from "the horse's mouth". The investment required is about $100 US at a minimum. Even less - US $34 now He did say a "timing receiver". That could mean a GPS receiver specifically set up to supply time, including an on board temp insensitive crystal to supply the time if the sattelite availability goes to low. There is no such thing as a "temp insensitive crystal"! A crystal can be placed in a tiny temperature controlled oven to achieve the *effect* of temperature insensitivity. Not true: Depending upon the cut, quartz crystals can be more or less temperature-sensitive, so it is in fact possible to get one that will wander less when the surrounding temperature changes. A TCXO avoids the problem, as you noted, by having a thermostat-controlled oven which keeps the temperature more or less constant. The most energy-efficient approach is to have a tiny temperature sensor on or near the crystal, then use a sw lookup table to compensate for temperature swings. Garmin have used this approach for many years in order to get sufficiently stable 10 MHz time bases in their GPSs. Terje -- - "almost all programming can be viewed as an exercise in caching" ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Odd offset for PPS DCD w/ Garmin GPS 18x LVC
On Apr 17, 10:03 am, lellis wrote: > > With the help of several radio-controlled clocks in my office, I > noticed that the local clock on my machine was occasionally off by > exactly one second (sometimes slow, sometimes fast). > > While I'm not sure this is the definitive answer, the following > changes seem to have helped: > > 1. I configured the Garmin to output both an RMC and a GGA sentence. > > 2. Using a small com port test program I wrote, I determined that the > GGA end-of-line is received about 850 ms after the leading edge of the > DCD pulse > > 3. I then modified my configuration file to include a time2 value of > 850 ms: > > server 127.127.20.1 mode 2 minpoll > 4 #mode 2, use GPGGA > fudge 127.127.20.1 flag1 1 time2 > 0.850 #time2 compensates for GGA offset > > I also deleted my drift file before restarting. > > I am now using a very recent build (4.2.7.p150) without apparent > problems. > > Larry Ellis As what will probably be a final update to this issue, the +125ms difference I reported initially *did* reoccur with 4.2.7p150. After several days of running with low milliseconds of difference between all reference sources, the +125s for the Atom PPS driver reappeared. Note, that the positive offset did not effect the user- mode PPS timing, which was still spot on: remote refid st t when poll reach delay offset jitter == *GPS_NMEA(1) .GPS.0 l9 16 3770.000 0.981 0.016 PPS(1) .PPS.0 l 10 16 3770.000 126.063 0.16 (other offsets < 5 ms) In effect, this tells me the offset between the user-mode PPS and the serialpps.sys PPS driver is about .125s (I was using flag1=0 to disable use of the kernel mode PPS). Since this odd recurrence was using software which heretofore had *not* shown the issue. I tried rebooting my system. It did not solve the problem (.125 offset still presented itself). I then cold-started the system, and the user-mode PPS and kernel-mode PPS offsets reverted to sub-millisecond range. So while the reason for this is unclear, a simple cold-start of the system accomplished what a warm reboot did not. This leads me to believe what I was seeing is likely a quirk of some kind in my hardware configuration. Thanks again to everyone who tried helping me with this. ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
Terje writes: > Depending upon the cut, quartz crystals can be more or less > temperature-sensitive, so it is in fact possible to get one that will > wander less when the surrounding temperature changes. It's possible to cut a crystal so that it has a near-zero temperature coefficient at a specific temperature[1], but the magnitude of the coefficient increases both above and below that temperature. [1] That is where you set your oven, of course. -- John Hasler jhas...@newsguy.com Dancing Horse Hill Elmwood, WI USA ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Bug 1700 - Clock drifts excessively at polling levels above 256.
On 2011-04-22, Mischanko, Edward T wrote: > 256. > > My system clock drifts excessively when polling above 256 in a Windows > environment, as much as 5 ms or more. I have made changes to > .../ntpd/ntp_loopfilter.c CLOCK_PLL, CLOCK_FLL, CLOCK_LIMIT, and > CLOCK_PGATE to address this problem. I realize the changes I have made > are global in nature and really only need changes in the Windows port. > I would welcome a patch to the Windows port to accomplish these changes > or any other changes that accomplish the 1 ms stability I have now > achieved. I hope Dr. Mills will have constructive comments on this > problem and proposed solutions. Does your system cpu use powersaving cpu frequency changes? Is it a virtual Windows machine? > */ ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Windows time question.
In article , david- tay...@blueyonder.co.uk.invalid says... > > > Hi David. Long time no speak. > > Oops, I missed the callsign! Hope all is well. > > > I'd ordinarily love to, but this is the works machine I carry arround > > places etc. Our illustrious IT droids have no interest in this, other > > than to "Flatten" the machine and re-install the OS. Anything outside > > the normal "Office" apps and "regular" OS issues, they have no knowlege > > of. Heck, I've fixed more IT problems round here than they ever will, > > (but I don't go near the office server!) > > > > Cheers. > > > > DaveB. > > I might even take the view that "your illustrious IT droids" aren't doing > their job properly if they aren't taking an interest in timekeeping to the > extent of replacing W32Time by NTP in their standard install procedure! > Perhaps timestamps of actions aren't critical your organisation. I > hope you may be able to convince them in due course. > > Having said that, I've not seen W32Time causing a crash, but my first step > might be to rename the appropriate branches of the registry to try and > make W32Time recreate them from scratch. > > 73, > David Hi All... It was a "clash" between XP's own W32Time, and National Instruments own Time serving/discovering component. That in turn got into the mix, after updating one of our principles sorftware products, that in turn blindly uptated all the installed NI stuff too. As their program *Needs* to use the NI thing, for now W32Time has been nobbled, and stability is resumed. I will be creating a batch file to invoke something at boot time, to prompt me to select what to use. I'm doing some sw work needing the NI drivers at the moment, but much of the time I can live without them (and recover 100's of MB ram too!) Thanks for the pointers people, and the snippets of info re the pool project. Regards. DaveB PS: Re the IT droids and doing their job. They were hired because they are cheap, need I say more... One of them cant even get into the building unless someone opens the door for him. So funny to watch... And the company trusts them with our server? Hmm ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
Re: [ntp:questions] Bug 1700 - Clock drifts excessively at pollinglevels above 256.
Your question is a very good one that I don't know the answer to. I have observed this behavoir while actually watching NTP Time Server Monitor by Meinberg, live. I didn't anticipate any power saving features as being active. I have seen a correction in the behavior by changing the PLL and FLL gains, as noted. I haven't specifially looked for this problem in other ports, only Windows and only on systems without a referrence clock. -Original Message- From: questions-bounces+edward.mischanko=arcelormittal@lists.ntp.org [mailto:questions-bounces+edward.mischanko=arcelormittal@lists.ntp.o rg] On Behalf Of unruh Sent: Saturday, April 23, 2011 1:20 PM To: questions@lists.ntp.org Subject: Re: [ntp:questions] Bug 1700 - Clock drifts excessively at pollinglevels above 256. On 2011-04-22, Mischanko, Edward T wrote: > 256. > > My system clock drifts excessively when polling above 256 in a Windows > environment, as much as 5 ms or more. I have made changes to > .../ntpd/ntp_loopfilter.c CLOCK_PLL, CLOCK_FLL, CLOCK_LIMIT, and > CLOCK_PGATE to address this problem. I realize the changes I have made > are global in nature and really only need changes in the Windows port. > I would welcome a patch to the Windows port to accomplish these changes > or any other changes that accomplish the 1 ms stability I have now > achieved. I hope Dr. Mills will have constructive comments on this > problem and proposed solutions. Does your system cpu use powersaving cpu frequency changes? Is it a virtual Windows machine? > */ ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions ___ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
