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 From:  Michael Sierchio <kudzu at tenebras dot com>
 To:  Fred Wright <fw at well dot com>
 Cc:  m0n0wall at lists dot m0n0 dot ch
 Subject:  Re: [m0n0wall] Re: time client/server proposal - comments please
 Date:  Wed, 25 Jun 2003 09:48:36 -0700
Fred Wright wrote:

> So he shows that with the 4501 running from an atomic clock synced to the
> PPS signal, the PPS samples are good.  Wow!  What a surprise! :-)
> Actually, I think the 4501 *can* do pretty well with this, but I wouldn't
> use *that* experiment to prove anything.

It proves you can have a 1us NTP stratum 1 server with a net4501.

> He is also depending on controlling one of the GP timers with the PPS
> signal, but the inputs with that possibility aren't available on the user
> I/O connector.  

This requires a low-profile RS422 card (which fits in the Soekris
case) for a long-run cable to the GPS.


>>I myself am content at the moment with the UltraLink M325.E,
>>supplying timecode and PPS signal to my 4501.  Had to write
>>a driver, the existing ulink driver doesn't work.
> 
> Using the PPS signal via an interrupt, occasional sampling, or sampling in
> a loop?

The PPS signal is delivered via RS232 interrupt on the DCD pin
and is handled by the ATOM_PPS driver of ntp, which the timecode
is handled by the ULINK driver -- it looks in the ntp config
as if you have two clocks, but they share the same device (/dev/cuaa0).

-- 

"Well," Brahma said, "even after ten thousand explanations, a fool is no
  wiser, but an intelligent man requires only two thousand five hundred."
                 - The Mahabharata