Re: Dropped frames in video capture process

H. Peter Anvin (hpa@transmeta.com)
13 Nov 1998 01:50:11 GMT

Followup to: <19981113112233.C29521@caffeine.ix.net.nz>
By author: Chris Wedgwood <chris@cybernet.co.nz>
In newsgroup: linux.dev.kernel
>
> On Thu, Nov 05, 1998 at 07:56:31PM +0000, Alan Cox wrote:
>
> > 8253 I think (well nowdays random bit of integrated chipset). The
> > gettimeofday() call reads it - but its actually quite slow to read.
> > Pentium and higher processors use the RDTSC CPU internal time clock
> > for the same purpose
>
> How does this for for SMP machines where presumably they can get out
> of sync. ?
>

They better not if they're to be used as real-time clocks! Anyway, it
is *VERY* unlikely they'll get out of sync (unless the TSC is broken
like on Cyrix chips) since virtually all SMP machines clock from the
same source.

Much harder is to get them synchronized in the first place.

-hpa

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