[ntp:questions] LOCL clock reachability not 377?

Rob nomail at example.com
Thu Jul 31 22:43:12 UTC 2014

William Unruh <unruh at invalid.ca> wrote:
> I think you need to read up on the cmos clock. As I said, it reports
> only the seconds, but is settable and "readable" to microseconds. 

The CMOS clock is running off a 32768Hz crystal, so no way it can be
more accurately set than 30us.

Even it could be possible in theory to set and read it accurately to
that value, apparently Linux does not do that.  That makes it questionable
to me if it can be done.  I could understand when Windows would not
exploit such a capability, when there is no monetary gain to be made.
But the Linux developers are too proud and too nerdy to skip such an

The fact that there is a microsecond-accurate API to set and read the
clock does not indicate anything.  Remember Linux can run on any platform,
and there may be other platforms, now or in the future, that can use
this accuracy.

In my experience, the clock always jumps a few hundred milliseconds
when rebooting a PC.

More information about the questions mailing list