[time-nuts] NMEA time
ch at murgatroid.com
Thu Nov 26 08:24:36 UTC 2009
Hal Murray wrote:
> Yes, mostly.
> PCs have two nasty disadvantages in terms of time keeping.
> One is that the CPU clock is typically using spread spectrum to make the EMI
> shielding (a lot) easier.
> The other is that the temperature at the crystal depends (a lot) on what the
> CPU is doing.
These are both problems, but the biggest issue in reducing jitter often
is minimizing SMM. Some SMI's can suck up 50 us at a go though most
are less. On some platforms you may see SMI's executing at a rate of
more than 1 Hz.
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