[BP] Informative Channel

[Steve Anderson <Steve.Anderson@xxxxxxxxxx>]

 

            All,

 

            At today’s meeting it seemed like much of the informative channel spec is being based on just one

set of simulations / analyses – those done by Joe Abler of IBM.  Other analyses – including stat eye -- have not been

as optimistic.  In particular, when significant amounts of Tx and Rx jitter are included, the number of channels

that “work” drops considerably.

 

In anderson_01_1104 I showed that I could get stat eye results that were better (more optimistic) than

Joe Abler’s for a small subset of channels, provided that I used assumptions similar to his.  When I use other

assumptions that I feel are reasonable, I get results that are worse than Joe’s.  It seems that small differences

in assumptions can lead to dramatically different results. (This probably doesn’t surprise anyone!)

 

One can argue about which set of assumptions should be used.  But this probably cannot be resolved,

since it is partly dependent on the implementation of the receiver, the IC packaging, etc.  A spectrum of chip

implementations will lead to a spectrum of results.

 

This leads to my first question:  Shouldn’t the informative channel be based on analyses

that are at the pessimistic end of the spectrum?

 

            Another question:  The LMS line in Richard’s presentation could lie right on the attenuation limit.  This

is about -30 dB at 5 GHz.  Richard purposely didn’t include any package effects.  But I’m going to assume that

these can add another 2 dB of attenuation.  With a Tx level of 800 mV ppd this gives us 20 mV ppd at the

receiver, or 10 mV pp single-ended.  Do other chip people think we can receive this?

 

            Regards,

 

            Steve A.