[ntp:questions] problem with synchronizing two comps to each other

Bjorn Gabrielsson bg at lysator.liu.se
Thu May 19 16:25:14 UTC 2005

Brad Knowles <brad at stop.mail-abuse.org> writes:

> At 2:37 PM +0200 2005-05-19, Mike wrote:
> >                                                            1 ms would
> >  be perfect. How can I do it? I suppose I need some Linux for it, are
> >  there any special distribution giving good precision?
> 	You could do it with Linux, but you'll probably want the
> PPSKit patches if you want to maintain any level of relative accuracy
> between the two machines over time, and this is still going to depend
> on the hardware.  Unpatched Linux and Windows have the problem that
> they tend to drop interrupts when they're very busy, and this destroys
> any ability to keep any kind of accuracy.

PPSKit-patch implements the kernel PPSAPI which is useful when you
have a good GPS with PPS-signal attached to the computer. In which way
does this relate to loosing timer interrupts? or the OPs question?

A normal Linux machine with no local reference clock (GPS) attached
_should_ _not_ be PPSKit-patched!

Loosing interrupts comes from having HZ set to high during high

> 	Solaris and the members of the BSD family tend to lose fewer
> interrupts than even a PPSKit-patched version of Linux, but you might
> have other reasons why you'd prefer to run Linux instead -- you'll
> have to make that decision yourself.

Lots of people run NTP on Linux with no problems. Lots of companys
sell Linux based NTP-servers.


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