Richard B. Gilbert wrote: > nemo_outis wrote: >> "Richard B. Gilbert" <rgilber...@comcast.net> wrote in >> news:tlsdnq2e26bblbnxnz2dnuvz_sydn...@giganews.com: >>> nemo_outis wrote: >> ... >>>> I fail to see the value or relevance of "500ppm satisfies 98% of >>>> computer clocks" if some other number, perhaps 5000 ppm, could >>>> satisfy yet even more than 98% of computer clocks with no downside - >>>> as indeed seems to be the case! Chrony, whatever its other merits >>>> and demerits, is an "existence proof" for this proposition. >> >> >>> I can't follow Dave's math but I'm reasonably sure that there is a >>> good reason for the 500 PPM limit. Since almost all computer clocks >>> can meet this criterion I'm not going to worry about it. >> >> Hmm, "faith-based" ntp? Not for me. If there is a "good reason" I'd >> like to hear it - 500 ppm has the smell of arbitrariness about it. >> >> >>> If you have a computer with a frequency error of more than 500 PPM, >>> you can either get it fixed or hack the ntpd code to allow +/- 600 or >>> 6000 or whatever PPM. >> >> Of course, one can hack the code. But one should not have to do this >> to overcome arbitrarily-imposed unjustified constraints. That Chrony >> can manage much more than 500 ppm may not not be absolutely probative >> in this regard but it sure is strongly indicative. >> >> Regards, >> >> >> >> >> >> >> > > I don't think Dave Mills would be willing to relax the 500 PPM limit. > I've been following this newsgroup for five or six years and this is the > first time that the 500 PPM limit has been questioned. > > Do you actually have a machine whose clock is in error by more than 500 > PPM? Or are you just making waves?
I have a couple with one over 500ppm and another over 1000ppm when on NetBSD 3. I'm sure both being due to the OS misidentifying the chips and getting the timer calibration wrong. I was able to pull both to within a few ppm by using custom kernels eg one pc with stock kernel was 60ppm out and "options TIMER_FREQ=1193250" vs default 1193182 gets it within a few ppm (now at -1.25ppm). The >1000ppm system is no longer in use, I'm not sure about the >500ppm box. NetBSD 5 seems to do a better job with calibration of the timer and on problem systems upgraded so far I've made no adjustments. David _______________________________________________ questions mailing list questions@lists.ntp.org https://lists.ntp.org/mailman/listinfo/questions
