David L. Mills wrote:
With all of the machines here, including FreeBSD, Solaris, HP-UX, SunOS, Tru64 and HP-UX, the loop response in steady state is as I reported earlier. The results with Linux are highly suspect, as at least in some cases the timer interrupt frequency has been changed significantly without compensation in the kernel parameters. I have recommended to avoid Linux in any case involving precision timekeeping.
Hello Dave, there is at least one issue with APIC routed interupts on linux running on nVidia nForce 1 and 2 based Boards resulting in a too fast and irregular clock. It seems the timer interrupt is handled _twice_ on occasion. I have A7N266-E and A7N8X-E boards produce this problem with various kernels in the 2.6.1n range. The same boards ran ntpd on linux 2.4 and no APIC routing just perfect. Symtoms: The clock starts to run ahead by ~8-900ppm resulting in hard correction of -.5 to -1.5 seconds every couple of hours. Adjusting the system tick value results in symetric corrections +.5 .. -.5 which would indicate an extremely unstable clock. This started out for me as a problem with ntpd not syncing BUT is now Linux/Hardware related with ntpd being the whistle-blower. One of the reasons i started reading this group some weeks ago. uwe _______________________________________________ questions mailing list [email protected] https://lists.ntp.isc.org/mailman/listinfo/questions
