[time-nuts] clock-block any need ?

Chris Albertson albertson.chris at gmail.com
Thu Dec 27 19:42:01 UTC 2012

Actually those "smart" interface and the low cost interface on dongles
use very dumb hardware and depend on software.  So they are not as
deterministic as you'd like.    The very best network hardware is
purpose built and expensive and does the timing in hardware.

I still think the lowest cos tmemthodis to distribute PPS to every
computer.  Then the only special wardware the PC needs is a serial

> A lot of the uncertainty is because of the "smart" Ethernet interface that
> tries to do stuff to offload the processor (buffering, etc.). This is one of
> the cases where old, less capable interfaces might do better.
> So, what about the USB-Ethernet dongles?  (I use them a lot at work to add a
> second interface for a laptop in test equipment setups, talking to a
> Prologix, for instance)
> Or, the Wiznet "Ethernet/IP stack" on a chip devices that talk via SPI, or
> basically, a serial port.
> https://www.sparkfun.com/products/9473 for a widget
> https://www.sparkfun.com/products/9471?  for the part
> http://www.saelig.com/product/BRD002.htm  a Ethernet to serial port board
> Some of these might have deterministic enough timing that it would be
> useful. They sure are cheap.
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Chris Albertson
Redondo Beach, California

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