Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt

Benjamin LaHaise
2005-07-13T19:39:10Z

On Wed, Jul 13, 2005 at 12:10:48PM -0700, Linus Torvalds wrote:
> Long-term time drift is a known issue, and is unavoidable since you don't
> even know the exact frequency of the crystal, since that is not only not
> that exact in the first place, it depends on temperature etc. So long-term
> time drift is something that we inevitably have to use things like NTP to
> handle, if you want an exact clock.

diz gave #kernel a good diatribe a few weeks ago about the headaches
associated with using the PIT as a clock source, with one of the more
interesting tidbits being that chipsets will pull the frequency higher
and lower at times in order to implement spread spectrum to comply with
RF emissions. The RTC doesn't suffer from this, but it only provides
HZ values which are powers of two. How bad would 256 Hz be?

-ben
--
"Time is what keeps everything from happening all at once." -- John Wheeler