[time-nuts] 1588 (was Re: NMEA Time)

[Christopher Hoover]

Hal Murray <hmurray at megapathdsl.net> wrote:

>
> 1) There is a group working on that level of accuracy.  It takes special 
> hardware that can put a time-stamp on a packet as it leaves or arrives.
>   http://en.wikipedia.org/wiki/Precision_Time_Protocol
>
>   
The newest Intel 82576 GigE controller supports 1588 by doing timestamps 
on the MII data.   It is a nice part.   Datasheet: 
http://edc.intel.com/Link.aspx?id=2372

You can this part on a PCIe card for < $170.  P/N E1G42ET and, e.g., 
available here:  
http://www.amazon.com/gp/product/B001KU90BO/ref=cm_sw_em_r_dp

As best I can tell, the crystal on the card is nothing better than what 
is needed to do GigE.  It is certainly not directly temperature 
compensated or oven-ized.

There is support in the most recent Linux kernel to relay rx and tx 
timestamps from a hardware timestamping capable controller such as the 
82576  to user space.

The software stack needed for a 1588v2 solution is missing at this 
point.  There are some sources for a 1588v1 ptp daemon on sourceforge, 
but it hasn't been hacked for NIC support.  (I have some early patches, 
but I'm not sure they are worth applying due to other problems with that 
code.)

-ch