[ntp:questions] Offset Average (Normal)?

unruh unruh at invalid.ca
Tue Mar 13 01:57:16 UTC 2012


On 2012-03-13, Alby VA <albyva at empire.org> wrote:
> On Mar 12, 7:21?pm, unruh <un... at invalid.ca> wrote:
>> On 2012-03-12, Alby VA <alb... at empire.org> wrote:
>>
>>
>>
>> > ?If your offset is between -400 to +600 ?s (microseconds), would you
>> > consider that Good, Bad, or Average?
>> > If it is less than Good, could something be tweaked to improve it?
>> > ntp.conf changes? cable changes?
>> > or I'm just SOL?
>>
>> What operating system? What is your server (network, wristwatch, gps,
>> pps?) For PPS you should be able to get +- 1us. for a server in Moscow,
>> +- 1ms.
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> > Stats
>> > --------
>> >http://godzilla.empire.org/
>> >http://www.pool.ntp.org/scores/63.251.89.141
>>
>> > assID=0 status=0115 leap_none, sync_atomic, 1 event,
>> > event_clock_reset,
>> > version="ntpd 4.2.... at 1.2349-o Mon Feb 20 22:00:33 UTC 2012 (1)",
>> > processor="amd64", system="FreeBSD/9.0-RELEASE", leap=00, stratum=1,
>> > precision=-19, rootdelay=0.000, rootdisp=1.082, refid=PPS,
>> > reftime=d308de90.7e20860b ?Mon, Mar 12 2012 16:44:00.492,
>> > clock=d308dec4.6a2aacac ?Mon, Mar 12 2012 16:44:52.414, peer=9406,
>> > tc=4,
>> > mintc=3, offset=0.081, frequency=-24.987, sys_jitter=6.771,
>> > clk_jitter=0.003, clk_wander=0.004
>
>
>
>  The Stratum 0 devices is SureGPS and its running on FreeBSD as the OS
> and AMD for the chip.

OK. Is it using its PPS or just the nmea sentences? If the latter then
100us is very good for a jitter. If the former it is very bad. (My
offsets on a chrony machine are standard deviation of about .8us, and on
an nptd machine, about 2us.-- using Linux and a serial interrupt with
pps_ldisc/pps_core driver on the former, and a parallel port interrupt
routine on the latter. 

If you are just using the sure nmea sentences, then you are getting far
better than expected. (man ms is more typical from SureGPS nmea only)




>
>
> FreeBSD godzilla.empire.org 9.0-RELEASE FreeBSD 9.0-RELEASE #0: Tue
> Feb 21 22:13:35 EST 2012  amd64
>
>
>
>



More information about the questions mailing list