[Beowulf] precise synchronization of system clocks

Lux, James P james.p.lux at jpl.nasa.gov
Tue Sep 30 15:18:04 EDT 2008




On 9/30/08 10:47 AM, "Lawrence Stewart" <larry.stewart at sicortex.com> wrote:

>
>
> On Sep 30, 2008, at 12:07 PM, Lux, James P wrote:
>
>>
>>
>>
>> On 9/30/08 8:37 AM, "Robert G. Brown" <rgb at phy.duke.edu> wrote:
>>>
>>
>> The grottiest grungy GPS receiver can probably do 100ns on its 1pps
>> tick,
>> and most are in the 20ns range.  There ARE receivers that have
>> systematic
>> errors (i.e. Some sort of sawtooth in the error) and, of course,
>> there are
>> countless schemes to compensate in one way or another.
>>
>
> So someone with some grad students and soldering irons should hook up
> the 1 pps
> output of a GPS to, say, the carrier detect pin on the unused RS232
> ports of all their
> nodes, and write some software...
>
> -Larry

Been done.  That's what ntpd has in it. Whether the implementation actually
deals with fielding the IRQ etc, I'm not sure. The Win NT 4.0
implementations did.


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