[ntp:questions] no ntp synchronisation: 2s to 6s time shift !
david at ex.djwhome.demon.co.uk.invalid
Fri Feb 15 22:35:56 UTC 2008
Thierry MARTIN wrote:
> If I understand your post, tsc is the same as acpi_pm ?
No. TSC, acpi_pm, the CTC based software clock that PCs have always
had, etc., are all fed from the same crystal, but run at different
multiples of that crystal's frequency. Only the battery backed clock
normally runs from a different crystal.
Software can get the readings wrong by missing ticks, or in the case of
the TSC counter, at least, by trying to work out the processor clock
speed, rather than being told it; typically they time the TSC clock
against the CTC one, during startup, and use that to calculate effective
CPU clock frequency.
The CPU clock frequency is slowed down by power management, so the TSC
rate can vary.
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