[ntp:questions] PSYCHO PC clock is advancing at 2 HR per second
Ron Frazier (NTP)
timekeepingntplist at c3energy.com
Tue Mar 20 18:21:32 UTC 2012
On 3/20/2012 1:25 PM, unruh wrote:
> On 2012-03-20, Ron Frazier (NTP)<timekeepingntplist at c3energy.com> wrote:
>> On 3/20/2012 2:25 AM, David J Taylor wrote:
>>> "unruh"<unruh at invalid.ca> wrote in message
>>> news:JDU9r.22132$_C5.11432 at newsfe09.iad...
>>>> Of course the question still is why in the world did the system go nuts
>>>> when it was on Local. That itself should not have happened.
>>> If some software had told the system clock to run fast, it simply
>>> stays running fast, even on Local.
>>> Ron is using a single GPS device, over USB, without the backup of a
>>> few Internet servers to stop such a thing happening, and the GPS has
>>> already shown itself to be problematical. NTP would normally have
>>> simply rejected the errant GPS data and not cause the PC clock to run
>>> wild, but without the Internet servers as backup, what is NTP to do?
>>> I don't think it has a choice other than to believe the GPS, even if
>>> it's incorrect or faulty.
>>> Ron, perhaps in the future you could adopt a similar configuration to
>>> one I've mentioned before - add some Internet servers with a long
>>> polling interval as a second opinion for NTP:
>>> server<ref clock stuff>
>>> server 0.us.pool.ntp.org minpoll 10 iburst
>>> server 1.us.pool.ntp.org minpoll 10 iburst
>>> server 0.uk.pool.ntp.org minpoll 10 iburst
>>> server 1.uk.pool.ntp.org minpoll 10 iburst
>>> using servers [network] local to yourself, of course.
>> Hi David T,
>> Eventually, I do plan to have the server preferences as follows:
>> Time server machine:
>> Internet as backup
>> Hypothetically speaking, what if I don't want it to distribute time if
>> it's working in internet mode?
>> Non time server machines
>> GPS (if attached)
>> Local time server (if available)
> Sorry to shout but NONONONONONONONONONO. Do not use Local time server
> ever, if by local time server you mean LOCL. If you mean a time server
> on your LAN, that is of course fine.
Poor choice of words. I meant LAN in that case.
>> Internet as backup
>> However, I only plan to do that after thoroughly testing the GPS by
>> itself for a week or two to see if it's stable. I originally had the
>> internet servers on with this unit. It completely surprised me by
>> having this tendency to drift apparently and have periodic heart
>> attacks. Unfortunately, this odd behavior may exist in all SIRF III and
>> possibly other SIRF units. It was only by turning off the internet
>> servers that I was able to get some clean graphs of exactly what the GPS
>> was doing. When I had the internet servers enabled, once the GPS
>> starting acting odd, which it shouldn't do at all, NTPD would clock hop
>> to the internet. Normally, that would be OK. However, as discussed
>> previously, even my errant GPS is more accurate over the short term than
>> the internet for me. With the internet conection, I get + / - 50 ms
>> variations in time over a span of an our. With the GPS, I get + / - 60
>> ms variations over several days, with a few wild corrections during its
>> heart attacks. Those are two bad choices, but I think I'd still rather
>> run on the GPS. The only way I can prevent clock hopping is by
>> noselecting the internet servers. Even if I end up with internet
>> servers turned on, which I expect to, I think it's much better to know
>> about these GPS anomalies before putting it into long term service.
>> Anybody considering using a SIRF III or maybe even any SIRF unit for
>> timekeeping should be warned by my experience, test the unit, and make
>> sure it's up to the task. These problems could even affect SIRF units
>> with PPS outputs, although I don't know. I'll probably decommission
>> this unit from timekeeping duty and relegate it to navigation duty,
>> although I'm not sure how trustworthy it is for that when it's throwing
>> a temper tantrum.
>> I've already committed to getting better (hopefully) equipment.
>> (Shipping from Hong Kong or where ever seems to take a LONG time when
>> you're waiting on something.) Hopefully, the Sure board will be much
>> more stable and reliable. I'm planning to do the same extensive testing
> Some apparently ship with bad antennas. Mine craps out often (delivering
> nothing to the unit) maybe some internal loose connection?
> (th blue light stops blinking).
>> on the Sure for a week or two. I'll start out just plugging the Sure
>> into my serial - USB converter using the same com port as the Globalsat
>> unit was running on. I want to see how it does with NMEA only data for
>> a while. I'm hoping NOT to see substantial drifting from UTC and NOT to
>> see any heart attacks every few days. I expect lots of jitter, since a
>> number of variable length sentences are being output. Then, I plan to
>> turn off all but GPGGA and test some more, and maybe tinker with the
>> baud rate. Then, if I can solder the board without killing it, I'll
>> engage PPS through the serial - USB port and test that for a while.
>> Then, I'll try it with PPS and real serial on my other computer, the
>> only one with a serial port.
>> Hopefully, when I'm done, I'll have a qualified unit running stably and
>> accurately for the whole network to use. I've acquired a case and some
>> hardware to mount the device similar to yours. Once I learned that it
>> was only 3" x 3", that made me nervous as far as soldering and all, but
>> we'll see what happens.
>> By the way, do you think I should update to Dave H's latest binaries?
>> I'm at 4.2.7p259 on Windows. Almost all these discussions have been
>> about Windows. Linux is a whole other ballgame. The NTPD there from
>> the repositories is about 2 years old, and I'm reluctant to go outside
>> the repositories because of the numerous problems it creates. One very
>> serious Linux user on a local message board said even he doesn't compile
>> his own programs because of possible problems. I tried it once and all
>> sorts of scripts and file locations that Ubuntu expects got broken.
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