[ntp:questions] NTP on CubieBoard

Rob nomail at example.com
Mon Oct 13 17:02:43 UTC 2014


David Woolley <david at ex.djwhome.demon.invalid> wrote:
> In this case, he is quoting a low jitter, which means that the offset 
> should also be low, unless ntpd has not yet acquired lock.  If it can 
> measure a stable jitter of around a microsecond, I think you can almost 
> certainly rule out a pure interrupt driven clock.  If the jitter 
> occasionally spikes, it could be that things are being synchronised to 
> ticks, but you would then see unusually high delays.

Remember it is PPS synchronized, not network synchronized.
The action of taking an interrupt, reading the current time and
storing it for later processing at kernel or user level can be performed
in well under a microsecond on a modern PC.

The question is if a Cubieboard can do that as well.


associd=0 status=011b leap_none, sync_pps, 1 event, leap_event,
version="ntpd 4.2.7p448 at 1.2483-o Sun Aug 24 10:33:47 UTC 2014 (1)",
processor="x86_64", system="Linux/3.2.0-4-amd64", leap=00, stratum=1,
precision=-23, rootdelay=0.000, rootdisp=1.000, refid=PPS,
reftime=d7e6840d.6b29e4dd  Mon, Oct 13 2014 19:02:05.418,
clock=d7e6840e.58db107a  Mon, Oct 13 2014 19:02:06.347, peer=5626, tc=4,
mintc=3, offset=0.000420, frequency=-17.882, sys_jitter=0.000709,
clk_jitter=0.001, clk_wander=0.000



More information about the questions mailing list