Hi Richard, > On Mar 11, 2022, at 6:51 AM, Richard Cochran <richardcoch...@gmail.com> wrote: > > On Fri, Mar 11, 2022 at 06:30:49AM -0800, Axel Simon wrote: > >> Sorry, I checked again and I stand corrected. We saw some offsets >> before we were able to monitor our system properly and it's still in >> my head that we can't get better than 2µs of noise. We are >> synchronizing the PTP clocks between different NICs using phc2sys >> and connect two x86 systems. > > Right, using phc2sys is not a great design for a GM. > > Why? > > because it uses SW time stamping. > > But that is not the fault of the i210 card. > > If you were to feed a 1 PPS from a GPS radio into the SDP of the i210, > for example, then you get your time error well below 1 usec. >
Earlier you wrote: > > For PCIe MACs, their PTP synchronization performance is NOT affected by PCIe > latency. > >> Interesting. For my application (telecom) I definitely need accuracy in the >> range of 1.5us. > > Easy to get the i210 to within a few dozen nanoseconds without doing > anything special. I find these statements a bit confusing. What do you mean by "PTP synchronization performance" if it is not the ability to synchronize to other NICs? "Not doing anything special" sounds to me like using phc2sys to synchronize various clocks in an x86 system. But then you say "phc2sys is not a great design for a" grandmaster. The only way to synchronize several devices with an accuracy of ~100ns using ptp4l seems to be (a) using several NICs, but synchronizing them via some PPS wires or (b) using a single NIC, and a PTP-enabled Ethernet switch I don't think that (a) classifies as "not doing anything special" and (b) is probably not what people think of naturally when they plan on using ptp4l as a boundary clock or master. Is there something I'm missing here? Is there any documentation or recommendation regarding the design of a high-accuracy linuxptp-based system? Cheers, Axel _______________________________________________ Linuxptp-users mailing list Linuxptp-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linuxptp-users
