[ntp:questions] Re: hardpps error

David L. Mills mills at udel.edu
Wed Feb 4 00:22:35 UTC 2004


I don't know what this display means; it certainly isn't in the code
that leaves here. The ntptime program produces a billboard explicitly
tailored to reveal what the PPS range-gate and frequency-grooming
algorithms find. Offhand, it looks like a really noisy PPS signal. If
you haven't got an oscilliscope, connect a pair of cheap headphones
accross the PPS plug and listen for one (loud) click per second and no
background noise or hum. If you haven't got headphones, any old
(off-hook) telephone will do. Best test instrument in the world.


Xuehuan Li wrote:
> i use motorola m12 card and pc running linux to found my ntp server. on one
> pc with linux 2.4.20-nano running on a pentium 166 mmx, there are many error
> like these:
> hardpps: bad pulse, delta = -9476359 ns
> hardpps: bad pulse, delta = -9476413 ns
> hardpps: new frequency 885742 >> 2 == 221435
> hardpps: new pps.freq=221435 (add 22487)
> hardpps: bad pulse, delta = -9866147 ns
> hardpps: PPSJITTER: jitter=9866147, limit=9861568
> while the filtoffset is up to hundreds and very unstable.
> i am sure the m12 card is a good one because it work perfect on another pc
> running the same kernel and the same ntpd.
> it's that means the pc's clock onboard is too bad to be used as an ntp
> server?
> bryant
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