[time-nuts] World's most accurate PC clock!

Poul-Henning Kamp phk at phk.freebsd.dk
Sun Jul 3 04:02:25 EDT 2005

In message < at>, "W. D." writes

>Is there a 'HowTo' for this somewhere?  How many pins are=20
>connected and to where?  Where do you mount the chip?  Any
>batteries involved?

This is a little bit beyond "HOWTO" stuff.

You need to find a suitable PLL chip.  ICST is a major manufacturer
of these.  Most of them have anti-DYI pin-spacing though.

Then you need to locate the Xtal on your motherboard which drives
the clocks.  Again, a good place to start is to look for a PLL
chip from ICST.  Usually there is a 14.318MHz xtal right next
to that, but some botherboards use different frequencies these
days and generate the 14.318MHz by PLL instead.

You can then either remove the existing xtal and feed your signal
to the right of the two holes (experiment or read datasheet for
the on-board PLL chip) or you can try override it while it remains
on the motherboard by feeding your signal into it.  Overriding
gives jitter and most modern motherboards don't like that.

Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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