FreeLists / si-list / [SI-LIST] Re: SATA eye diagram - how much is too much

[Istvan Novak <Istvan.Novak@xxxxxxx>]

Charles,

I think this may be a grey area, where depending on the what is exactly 
you measure and what are the quality/reliability expectations of your 
system, you may need to take a further look.

One could argue that one violation (which may or may not turn into an 
error in your system) per minute is not a big deal, and it is probably 
true that if errors do not line up into longer bursts, it would be hard 
to notice in a user-run system without careful measurements.  However, 
the performance  numbers extrapolated from a relatively short period of 
time assume that the statistics of noise/interference causing the 
violations/errors do not change with time.  In general, this is not 
true.  A simple example is violation/error introduced by data-dependent 
crosstalk and ISI, induced for instance from a DIFFERENT, UNRELATED 
subsystem.  Unless you make sure that the neighboring subsystems, which 
may induce noticeable noise onto your link under test are really 
excercised over all of their possible combinations of activities, it is 
very questionable to extrapolate from short samples.

Regards,

Istvan


Grasso, Charles wrote:
> Greetings!
>  
> I have a question regarding the interpretation of the eye diagram data vis a
> vis
> SATA.
>  
> How many violations of the eye does it take before a design is brought to a 
> screeching halt? A follow up question:
>  
> Can eye violations be graded in terms of severity based on the location
> of the violation (that is : at the outer bounds, or the internal eye
> trapezoid )?
>  
> The basis of this question (naturally) is that I have SATA data that have
> exactly 
> one 1 violation at the outer bound of the eye at 1 minute of data capture.
> Typical go/no go specification will determine that to be a fail. I am not so
> sure.
> Any insight would be greatly appreciated.
>  
> Thanks
>  
> Best Regards
> Charles Grasso
> Senior Compliance Engineer
> Echostar Communications Corp.
> Tel:  303-706-5467
> Fax: 303-799-6222
> Cell: 303-204-2974
> Email: charles.grasso@xxxxxxxxxxxx; <mailto:charles.grasso@xxxxxxxxxxxx; >
> Email Alternate: chasgrasso@xxxxxxxx <mailto:chasgrasso@xxxxxxxx> 
>  
>  
> 
> 
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-- 
Istvan Novak            Sun Microsystems, Inc.
Istvan.Novak@xxxxxxx    Workgroup Servers, BDT Group,
                        One Network Drive, Burlington, MA 01803
                        Phone: (781) 442 0340

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