On Wed, Jul 24, 2019 at 12:44:26PM +0200, Mike Cook wrote: > > Le 24 juil. 2019 à 11:19, William Unruh <un...@invalid.ca> a écrit : > >> > >> The hardware under consideration can time the pulse arrivals more > >> precisely than the interrupt delivery time, thanks to special hardware. > > That tickled a grey cell. There was/is a timing product family > bc635/637 time and frequency processors sold by Microsemi which can > timestamp a PPS input event to 100ns resolution. Various OS drivers > are available, but no ntp refclock driver AFAIK.
There may be cheaper and better options for a highly accurate NTP server today. For example, the I210 NIC supports HW timestamping and has SDP pins which can timestamp PPS. The same device/clock is timestamping packets and pulses, so there are no asymmetries due to PCIe, etc. This is supported in existing software. Timestamps in NTP packets can have sub-100ns accuracy. In this case it would make sense to apply the corrections from GPS, but I'm not sure how it would be implemented. (I'm responding to the newsgroup as messages from the mailing list are not forwarded back. People asking questions in the newsgroup may want to check the archives of the list to see if anyone responded there.) -- Miroslav Lichvar _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions