Messages in this thread | | | Subject | Re: Time precision, adjtime(x) vs. gettimeofday | From | Benjamin Herrenschmidt <> | Date | Wed, 08 Oct 2003 18:22:58 +0200 |
| |
> 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.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |