Edward T. Mischanko | Maintenance Technician, Electrical ArcelorMittal Burns Harbor Finishing | 250 W. US Highway 12 Burns Harbor, IN 46304-9745 T +1 219 787 3601 | F +1 219 787 4510 www.arcelormittal.com
_____________________________________________ From: Mischanko, Edward T Sent: Thursday, April 21, 2011 12:02 PM To: 'questions@lists.ntp.org' Subject: Bug 1700 - Clock drifts excessively at polling levels above 256. My system clock drifts excessively when polling above 256 in a Windows environment, as much as 5 ms or more. I have made changes to .../ntpd/ntp_loopfilter.c CLOCK_PLL, CLOCK_FLL, CLOCK_LIMIT, and CLOCK_PGATE to address this problem. I realize the changes I have made are global in nature and really only need changes in the Windows port. I would welcome a patch to the Windows port to accomplish these changes or any other changes that accomplish the 1 ms stability I have now achieved. I hope Dr. Mills will have constructive comments on this problem and proposed solutions. /* * This is an implementation of the clock discipline algorithm described * in UDel TR 97-4-3, as amended. It operates as an adaptive parameter, * hybrid phase/frequency-lock loop. A number of sanity checks are * included to protect against timewarps, timespikes and general mayhem. * All units are in s and s/s, unless noted otherwise. */ #define CLOCK_MAX .128 /* default step threshold (s) */ #define CLOCK_MINSTEP 300. /* default stepout threshold (s) */ #define CLOCK_PANIC 1000. /* default panic threshold (s) */ #define CLOCK_PHI 15e-6 /* max frequency error (s/s) */ #define CLOCK_PLL 1.8 /* PLL loop gain (log2) */ #define CLOCK_AVG 8. /* parameter averaging constant */ #define CLOCK_FLL .001 /* FLL loop gain */ #define CLOCK_FLOOR .0005 /* startup offset floor (s) */ #define CLOCK_ALLAN 11 /* Allan intercept (log2 s) */ #define CLOCK_DAY 86400. /* one day in seconds (s) */ #define CLOCK_JUNE (CLOCK_DAY * 30) /* June in seconds (s) */ #define CLOCK_LIMIT 15 /* poll-adjust threshold */ #define CLOCK_PGATE 2. /* poll-adjust gate */ #define PPS_MAXAGE 120 /* kernel pps signal timeout (s) */ #define FREQTOD(x) ((x) / 65536e6) /* NTP to double */ #define DTOFREQ(x) ((int32)((x) * 65536e6)) /* double to NTP */ _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
