On 2011-05-05, Chris Albertson <albertson.ch...@gmail.com> wrote: > The most simple explanation is that the PPS signal out of the clock is > just about as poor as NTP is reporting it to be. In other words > everything is working fine. Nothing is wrong with your cable or with > NTP or with Windows. Until some tests show otherwise I think it is > best to assume the PPS signal going into the PC is close to how NTP is > describing it. > > If you need better buy a GPS. You can get setup with one that does > works at the nanosecond level for under $100.
Uh, no. There is no way of getting the signal into the computer with nanosecond accuracy. 1usec is about it. The interrupt service routines, if you use a specialised driver for some interrupt driven card, will take about 1usec to service the interrupt. Thus while the card may deliver a pulse whose leading edge is within say 50ns of the correct time that is irrelevant if the computer itself cannot respond fast enough. But I agree, with a GPS you can get usec accuracy in the time delivered for less than $100. > > On Thu, May 5, 2011 at 9:32 AM, Ken Link <kl...@numberzero.org> wrote: >> Assuming the Delay, Offset, and Jitter column units are msec, after >> letting it run overnight and half of the next day I still see PPS with >> 0 delay, 4.559 msec offset, and 3.123 msec jitter. >> >> The PPS source is the Meinberg TCR511PCI card, as seen here: >> http://www.meinberg.de/english/products/tcr511pci.htm >> > _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
