[ntp:questions] Re: NMEA refclock - PPS not working

Hal Murray hmurray at suespammers.org
Tue May 16 05:31:35 UTC 2006


>I have an nForce 4 board here, and it has a "spread specturm" option in
>the BIOS. I believe this option "fuzzes" the processor clock by a few
>percent in either direction, in order to avoid outputting lots of RF
>noise on a single frequency. This option was on by defualt on my board.
>You might want to make sure it is disabled, as it could certainly cause
>ntpd to do Bad Things.

It's a common trick in modern PCs.  I doubt if it causes any troubles.

Note that the clock only gets stretched.  If you shrink it you violate
timings.  It's pretty easy to measure.  Just compare the cycle counter
with the clock and notice that your clock is running a bit slower than
expected.

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