Hi > On Nov 9, 2014, at 3:31 PM, Chris Albertson <[email protected]> wrote: > > On Sun, Nov 9, 2014 at 10:11 AM, Bob Camp <[email protected]> wrote: > >> >> That may (or may not) give you the best ADEV on the output. My guess is >> that the filtering algorithm will need to be a bit more complex. NTP’s aim >> is mainly to throw out bad clocks and pick one as best. We would more >> likely want to combine the outputs and use all of the good clocks we have. >> The idea is to improve on the ADEV of the *best* source you have available. >> > > No, not "pick one as best". NTP does not pick the best clock. NTP finds > the subset of clocks that track each other. Clocks are allowed to enter > and leave this set. NTP then computes a weighted average of the clocks in > the set. Pretty much what you said you wanted. > > These two algorithms are used. Conceptually that are run one after the > other but actually they run together in a loop forever > 1) clock selection <http://www.eecis.udel.edu/~mills/ntp/html/select.html> > 2) clock cluster <http://www.eecis.udel.edu/~mills/ntp/html/cluster.html>
The clock that’s in the middle of the cluster is the one that is “best” and gets flagged as such. Bob > > You would not want to use this exact algorithm but something like it. I > think the basic idea is simple: Reference clocks should tend to cluster > around correct behavior. In other words our set of reference clocks is not > biased. I don't think there is any way to detect bias unless you add more > reference clocks. > > I would very much avoid an FPGA based CPU. You likely will need to add both >> flash and ram to the FPGA. Once you are done, you have a $30 gizmo that >> replaces a $1 chip. You also have a tool chain for your code that is far >> from “low barrier to entry”. It’s a great solution for something like video >> processing that needs TONS of bandwidth. We are very much on the other end >> of that stick. >> > > I agree. Unless the whole this is FPGA based and you have enough free > gates. Otherwise it is not good to use something so complex to simulate a > $2 part. > >> >> -- > > Chris Albertson > Redondo Beach, California > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
