Re: Time precision, adjtime(x) vs. gettimeofday

[Benjamin Herrenschmidt]

> Well, it it affects gettimeofday which has a precision of 1 part in
> 10000 (100 ppm), it means that our boot time timebase calibration was
> not very good to start with, on my set of running VME machines I have
> the following (values in ppm):
>
> ../..

Boot time calibration can't be perfect... I depends very much on the
quality of what your are calibrating against, and the bus path to it.

On most pmacs, I'm calibrating either against a VIA timer which isn't
_that_ good or on OF value (which are themselves calibrated, I think,
against the KeyLargo timer).

On all cases, those will drift some way from what the NTP server will
give, either a lot or not, it will. So we may end up adjusting our
kernel rate and thus opening a window for the problem.

Ben.

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