[ntp:questions] PSYCHO PC clock is advancing at 2 HR per second

Chris Albertson albertson.chris at gmail.com
Tue Mar 20 20:06:52 UTC 2012


Ron,

I think the below is "correct enough" but accuracy is only one dimension of
NTP server performance.    As you have found one other dimension is
"reliability".

It does little good to have a system that is running at pico-second level
But jumps ahead two years at rare unpredictable times.   (It is kind of
like the race car that goes 200MPH but the engine blows every third race.)

It would be interesting to make a table like yours but to list varying
degrees of reliability.

On Tue, Mar 20, 2012 at 12:09 PM, Ron Frazier (NTP)
>
> Speaking only regarding Windows systems for a moment:
>
> So, let's say a person needs + / - 100 ms performance from UTC.  He can
> use the internet, even with wireless, and multiple routers, like I have.
>  Or he could use even a USB only GPS if there is a reason.
>
> Say he needs + / - 20 ms performance.  Internet may be an option depending
> on the circumstances.  GPS might be a better option depending on the GPS.
>
> Say he needs + / - 1 ms performance.  Internet is probably not an option,
> at least in my experience and my location.  USB only GPS with PPS through
> the serial - USB converter might work.  Serial GPS with PPS would work.
>
> Say he needs + / - 20 us performance.  Excluding the realm of rubidium
> standards and such, serial GPS with PPS is probably the only option.
>
> Chris Albertson
Redondo Beach, California


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