Re: clock troubles

[Marty <martyb@ix.netcom.com>]

Glenn English wrote:
> The system clock on one of my machines is running way slow. If I
> repeatedly run 'date' the second changes once every 3 or 4 seconds.
> ntpdate will bring it into line, but ntpd can't keep it there.
>
> I don't understand how this can happen. My experience with digital
> electronics says that things almost never work half-way; they're fine,
> or they're dead. Anybody know what the system clock actually is? A
> counter counting the line frequency?? A divider off the CPU clock?
>
> There was a power failure this morning, long enough to drain the UPSes
> and stop all the computers. Then when I started bringing things back up,
> I could just barely catch the aroma of overheated electronics -- so it
> could be hardware. It could also be my imagination.

I have an old, slow system (100MHz) that also doesn't keep time with the ntp server
with kernel 2.6.8, but does with 2.4.27.  I think the relevant difference between
these two kernels is the change from 100Hz to 1000Hz timer tick rate.  (See my post
about the problem several weeks ago.)  My working theory is that the slow CPU cannot
keep up with the 1000Hz tick rate and is losing ticks, since the time problem seems
to vary directly with increasing CPU load.  I have not yet reported this as a bug.