[ibis-macro] Re: Samples_per_bit question

  • From: "Muranyi, Arpad" <Arpad_Muranyi@xxxxxxxxxx>
  • To: "ibis-macro@xxxxxxxxxxxxx" <ibis-macro@xxxxxxxxxxxxx>
  • Date: Wed, 20 Jul 2011 21:47:23 +0000

Mike, Scott, Kumar,

First, the models I ran into recently were brand new models,
probably not even released yet.  I don't know the reason, but
it appears that the problem might be learning curve related
on the author's part.

This is why I tend to not agree with requiring the models to
do the re-sampling for themselves.  This is extra burden on
the model makers which we should try to avoid.  EDA vendors
are probably better at writing such algorithms, and if the
EDA vendor knows what sampling rate the model works with
(using the proposed required and reserved parameter for that),
they can do the re-sampling for the model if necessary before
executing it.

I would prefer to put this Sample_per_bit parameter in the
AMI spec, and make it required, reserved.


Ambrish,

I agree that "to require a certain samples_per_bit for the model to work is not 
good"
but it does happen unfortunately.  But I am not sure what you mean
by "We can deal with this at a tool level and not put anything in the spec".  
How would
the tool know how to deal with a certain model if it doesn't know
what sample rate(s) the model works with?  I think the only way
a tool can deal with this if every model would be required to
tell the tool with a reserved parameter what its sampling rate
needs/capabilities are.

Thanks,

Arpad
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From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] 
On Behalf Of Mike Steinberger
Sent: Wednesday, July 20, 2011 4:17 PM
To: ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: Samples_per_bit question

Scott-

Moving forward, we could conceivably take the approach you suggest. That 
approach still doesn't address the models that are already out there, however. 
I, for one, don't want to be in the position of telling users they can no 
longer run models that they've been running for years. (Actually, I know for a 
fact that I personally won't be in that position, so it's really a choice for 
others to make.)

Mike S.

On 07/20/2011 03:53 PM, Scott McMorrow wrote:
Ambrish

Why not go the other direction, which would be to explicitly require that the 
model perform sample rate conversion to any sample rate.

Scott




Scott McMorrow

Teraspeed Consulting Group LLC

121 North River Drive

Narragansett, RI 02882

(401) 284-1827 Business

(401) 284-1840 Fax



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On 7/20/2011 4:49 PM, Ambrish Varma wrote:
I think we all agree that to require a certain samples_per_bit for the model to 
work is not good. We can deal with this at a tool level and not put anything in 
the spec as this will most definitely give it more prominence. In other words, 
model makers will feel compelled to 'do something' with this parameter.
My 2 cents.

-Ambrish.




[cid:image002.gif@01CC46FB.CCC6FBB0]



Ambrish Varma   |  Member of Consulting Staff

P: 978.262.6431   www.cadence.com<http://www.cadence.com>










________________________________
From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> 
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Dmitriev-Zdorov, Vladimir
Sent: Wednesday, July 20, 2011 4:25 PM
To: msteinb@xxxxxxxxxx<mailto:msteinb@xxxxxxxxxx>; 
ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: [ibis-macro] Re: Samples_per_bit question


Agree,



We also encountered with such models. The problem is when something does not 
work it is difficult to guess what's the problem and even after that it takes 
several tries to find an appropriate parameter.



Vladimir


From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx> 
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Mike Steinberger
Sent: Wednesday, July 20, 2011 2:18 PM
To: ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: [ibis-macro] Re: Samples_per_bit question

Kumar-

We agree with you in principle, and on the two occasions (years ago now) when 
we encountered a model that required a specific number of samples per bit, we 
did ask the model developers to make their models more general. Unfortunately, 
neither the IBIS spec nor any customer required them to support an arbitrary 
number of samples per bit, so the model developers did not accept our 
suggestion.

These models have now been in widespread use for several years. Given that, how 
should we handle the problem? To date, the solution we've proposed is the 
Samples_per_bit reserved parameter.

Thanks.
Mike S.

On 07/20/2011 03:07 PM, ckumar wrote:

the ami model should treat the waveforms as continuous. They should

resample it inside the model for their requirements.

Requiring specific sample size is an unnecessary constraint.

On Wed, 20 Jul 2011 19:44:03 +0000, "Muranyi, Arpad"

<Arpad_Muranyi@xxxxxxxxxx><mailto:Arpad_Muranyi@xxxxxxxxxx> wrote:

Hello everyone,



I recall that we asked Walter to remove the proposed Samples_per_bit

Reserved AMI parameter from BIRD 121, which he did in BIRD 121.1.

What I don't remember is whether we made this request because we

decided that we didn't want/need this reserved parameter in the AMI

specification at all, or whether we just didn't want to propose this

in BIRD 121, since it seemed unrelated to the rest of the BIRD 121

content.  Could someone please refresh my memory on that?



The reason I am asking is because just recently I ran across a couple

of AMI models which only work at certain samples per bit settings

but there was no documentation that I am aware of that came with the

model that stated that.



I am not sure if this was done intentionally by the model's authors,

but it seems that a required reserved parameter would at least serve

as a reminder to the model makers to document the value at which

their model works, if not remind them to write models that work at

any reasonable samples per bit values.



Based on this experience I tend to feel that a required, and reserved

parameter for Samples_per_bit would be very useful in the AMI spec...



Comments, suggestions are welcome.



Thanks,



Arpad

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