Re: [IBIS] *-AMS solves all of IBIS problems?

From: Scott McMorrow <scott_at_.....>
Date: Mon Apr 04 2005 - 12:27:00 PDT
Arpad,

*See my comments in blue:*

scott


Muranyi, Arpad wrote:

>Syed, Scott,
>
>I renamed that ugly subject line of mine... and would like to
>respond to this quick quote from Scott:
>
>  
>
>>...that the implied assumption that AMS modeling will somehow solve
>>all of our IBIS modeling problems is sorely mistaken.
>>    
>>
>
>I will take that blame on myself, because I feel quite optimistic
>about AMS these days, and may have said things that come across
>that way.
>
>I would like to ask Scott, please give some examples for why not.
>Or can I take your next sentence as an example?
>
>  
>
*Thus far, all of the "correlations" between *-AMS and either HSPICE or 
measurements have been rather simplified models.  Quite frankly, when 
you take a look at the Altera correlation, it ain't that close to 
measurement either, and it's not clear whether it is the interconnect 
modeling and simulation that is at fault, the power delivery modeling, 
or the device modeling.  We've found not just a few SerDes drivers which 
operate quite a bit differently than even their HSPICE models of just 
the driver would predict, when transmitting long differential data 
streams.  We suspect that the differences between modeling and 
measurement occurs because of lack of package power delivery modeling, 
and integration of this  into the driver model.  Once you add the full 
power delivery path and a quad-SerDes into the model, will the results 
be that encouraging?  I hope so. However, I am on record as having 
misgivings. Personally, I think that correlations of *-AMS should start 
at this level of complexity, so that a fully correlated solution is 
shown, before delving into model order reduction techniques to speed  up 
performance.*
.

>>Interaction between the silicon and that pesky passive
>>interconnect must be dealt with simultaneously, if we are to believe
>>that our simulation results have true high-fidelity to measured
>>results.
>>    
>>
>
>Why would this not be solvable by writing models with *-AMS?
>The way I see it, this is really just up to the model writer
>what they characterize and how it is written up in the *-AMS
>model.  It doesn't seem to be a language limitation to me.
>Am I missing something?
>  
>
*You are not missing a thing. I believe that *-AMS can be used to model 
anything.  The question is whether it will be competitive with HSPICE in 
performance once all of the imporatant details (gate modulation, 
feedback, power starvation, resonances, frequency dependent power 
delivery, etc ...) are modeled.  This is the unresolved question.  My 
gut tells me no, since *-AMS is designed to be a more general language.  
I will be happy to learn that I am wrong.  *

>Arpad
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Received on Mon Apr 4 12:27:20 2005

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