[ntp:questions] site with lots of GPS's and accessories
unruh at invalid.ca
Mon Mar 19 21:55:32 UTC 2012
On 2012-03-19, Dennis Ferguson <dennis.c.ferguson at gmail.com> wrote:
> On 19 Mar, 2012, at 13:58 , Alby VA wrote:
>> Compared to this history of Atomic Clocks at NIST
>> and this chart of accuracy, I'd say my NTP Server is
>> in the 50yrs behind the curve. lol At least its portable.
>> History: http://www.nist.gov/pml/div688/grp40/nist-clocks.cfm
>> Chart: http://upload.wikimedia.org/wikipedia/commons/9/9a/Clock_accurcy.jpg
> You could do a lot better with hardware designed to timestamp
> an edge. The timestamp-in-an-interrupt-routine thing is a
> hack that has never been outgrown.
> This can be done with a peripheral interface designed for the
> purpose, though this still leaves one with the problem of
> transferring the peripheral clock's time to the computer (the
> latter also seems to be the problem with IEEE 1588). A
> better way would be for Intel (or someone) to devote a CPU
> pin to receiving signal transitions, along with the logic
> to sample in hardware and deliver to software the contents
> of the TSC at the time of an edge. Then there'd be a
> market for "timekeeping" motherboards, with that pin wired
> to an appropriate receiver with an input connector and maybe
> with a better quality crystal (with a synchronization
> frequency input?) clocking the CPU complex.
Meanwhile in order to increase energy saving and decrease narrowband
noise, CPUs are going for spread spectrum timing and tickless clocks.
> Dennis Ferguson
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