System clock frequency offset changes drastically across reboots
[ Re-sending... Please feel free to comment, even if you don't have "The Solution". I'd just like to get some feedback. ] Hello everyone, I'm using 2.6.20.7-rt8 on a P3. I've noticed that the frequency offset of my system clock (computed either by ntpd, or by hand) changes drastically across reboots. By drastically, I mean +/- 60 ppm every time I reboot. Apparently this is caused by some imprecision in the frequency estimation done in calculate_cpu_khz() (arch/i386/kernel/tsc.c) My brutally crude work-around was to skip the computation altogether and hard-code the "correct" value for cpu_khz. http://linux.kernel.free.fr/cpu_khz.adlink Has this issue been investigated more thoroughly by other users? Regards. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: System clock frequency offset changes drastically across reboots
[ Expanding recipients list to include NTP mailing list ] John Sigler wrote: I'm using 2.6.20.7-rt8 on a P3. (But some ntpd users have reported the problem with mainline kernels and different versions.) I've noticed that the frequency offset of my system clock (computed either by ntpd, or by hand) changes drastically across reboots. By drastically, I mean +/- 60 ppm every time I reboot. Apparently this is caused by some imprecision in the frequency estimation done in calculate_cpu_khz() (arch/i386/kernel/tsc.c) My brutally crude work-around was to skip the computation altogether and hard-code the "correct" value for cpu_khz. http://linux.kernel.free.fr/cpu_khz.adlink Has this issue been investigated more thoroughly by other users? Is there, perhaps, more appropriate a forum to discuss such matters? Regards. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: System clock frequency offset changes drastically across reboots
[ Expanding recipients list ] John Sigler wrote: I'm using 2.6.20.7-rt8 on a P3. But some ntpd users have reported the problem with mainline kernels and different versions. I've noticed that the frequency offset of my system clock (computed either by ntpd, or by hand) changes drastically across reboots. By drastically, I mean +/- 60 ppm every time I reboot. Apparently this is caused by some imprecision in the frequency estimation done in calculate_cpu_khz() (arch/i386/kernel/tsc.c) My brutally crude work-around was to skip the computation altogether and hard-code the "correct" value for cpu_khz. http://linux.kernel.free.fr/cpu_khz.adlink Has this issue been investigated more thoroughly by other users? Regards. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
System clock frequency offset changes drastically across reboots
Hello everyone, I'm using 2.6.20.7-rt8 on a P3. I've noticed that the frequency offset of my system clock (computed either by ntpd, or by hand) changes drastically across reboots. By drastically, I mean +/- 60 ppm every time I reboot. Apparently this is caused by some imprecision in the frequency estimation done in calculate_cpu_khz() (arch/i386/kernel/tsc.c) My brutally crude work-around was to skip the computation altogether and hard-code the "correct" value for cpu_khz. http://linux.kernel.free.fr/cpu_khz.adlink Has this issue been investigated more thoroughly by other users? Regards. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
