Re: [BP] ATCA Test Channels / FEXT
Charles,
I could tease you and say yes, but I am just not that cruel.
The data provided by Tyco and Intel is correct for scenarios where there
are more than 8 pair between a given line card and fabric. This is not
the case for ATCA however, where there is a total of 8 pair between a
given line card and fabric. Therefore, we don't want the assumptions we
made with the channels to reflect negatively on ATCA, as they may not be
reflective of the channel conditions for ATCA. This will become an even
bigger issue as we move forward with the worst casing of simulations
which are or near underway.
John
-----Original Message-----
From: Charles Moore [mailto:charles.moore@avagotech.com]
Sent: Sunday, April 02, 2006 9:56 PM
To: DAmbrosia, John F
Cc: STDS-802-3-BLADE@listserv.ieee.org
Subject: Re: [BP] ATCA Test Channels / FEXT
john,
Does this mean that you are planning on recommending a change to
the ICR spec?
charles
DAmbrosia, John F wrote:
> All,
>
> Rich Mellitz and I were reviewing the channels being discussed, and
were
> reviewing the crosstalk aggressors. We discovered a potential issue
> with the FEXT data submitted for the ATCA channels. In Tyco's data it
> is assumed that the two FEXT aggressors are equivalent, while in the
> Intel data the FEXT data was generated where all aggressors came from
> the same line card. For a real ATCA system the two above scenarios
are
> incorrect. In the ATCA system channels are based on the 8
differential
> pair from a single line card to the fabric. Thus, if you look at the
> fabric a single Rx pair would be hit on one side from an aggressor
> originating from the same line card and another aggressor originating
> from a different line card. From initial simulations Rich has done,
the
> value of FEXT in a net where a single connector is shared is
> significantly lower than a case where two connectors are shared.
> Therefore, one of the FEXT aggressors is probably less than what was
> originally anticipated. Tyco is currently modifying line cards to
> provide test data that shows this effect. Hence, we should gain some
> further margin for ATCA applications by reducing one of the 3
> contributors.
>
> Cheers!
>
> John D'Ambrosia
>
>
--
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