In ntp_proto.c the delay and offset are computed as follows: t34 = t3 - t4;
t21 - t2 - t1; p_del = t21 - t34; offset = (t21 - t3)/2.; where t1 = client send time t2 = server receive time t3 = server send time t4 = client receive time. However, t1 and t4 are not really in seconds if the client clock is slewing. That is, the difference t4 - t1 will be shorter than seconds if the clock is being slowed down and larger if the clock is being sped up. Hence the clock slew may be a source of variation that is not presently being accounted for. One some systems the frequency of the Performance Counter (PC) is constant because it is driven by the High Performance Event Timer (HPET). And according to one article on the Internet, the PC can be made to be driven by the HPET on Win 8 by this edit: " run cmd as admin and paste 'bcdedit /set {current} useplatformclock Yes'". Would NTPD have less variation in offset and delay if, say, t4 were measured by the difference in PC readings between the time t1 is measured and the time T4 is presently measured? Charles Elliott _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions