[ECOS] More Wallclock questions

Jesper Skov jskov@redhat.com
Wed Dec 5 02:04:00 GMT 2001

On Wed, 2001-12-05 at 10:11, Damir Salantic wrote:
> So, kernel realtime clock is actually synchronized with wallclock in the
> initialization and later when you want to read wallclock you actually read
> kernel clock.

Note that on some platforms the kernel clock may not be accurate over
long periods of time.

This can be caused by (a) inaccuracy in timer programming [even if it's
accurate to 0.1% of the 100Hz ticks, the error will accumulate over
time], and (b) delays in reloading the timer [some platforms do not have
automatic reload of the timer counter, so disabling interrupts may cause
(minimal) timer drift, which again accumulates over time].


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