[ibis-macro] Re: Samples_per_bit question

  • From: ckumar <ckumar@xxxxxxxxxxx>
  • To: <Arpad_Muranyi@xxxxxxxxxx>
  • Date: Wed, 20 Jul 2011 15:07:30 -0700

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making it required reserved parametr is perpetuating an extremely poor
practice

On Wed, 20 Jul 2011 22:04:59 +0000, "Muranyi, Arpad"
<Arpad_Muranyi@xxxxxxxxxx> wrote:
> Kumar,
> 
> The EDA tool can resample the waveform(s) between
> the Tx and Rx calls according to their own needs...
> 
> Arpad
> ====================================================
> 
> -----Original Message-----
> From: ckumar [mailto:ckumar@xxxxxxxxxxx] 
> Sent: Wednesday, July 20, 2011 5:00 PM
> To: Muranyi, Arpad
> Cc: ibis-macro@xxxxxxxxxxxxx
> Subject: Re: [ibis-macro] Re: Samples_per_bit question
> 
> I do not agree with that. 
> What happens if the tx and rx requires different samples per bit? Things
> can get convoluted very fast.
> 
> That is why the emphasis should be on that the models are always seeing
> continuous signals. Any way that is what devices do in real life too.
They
> sample a continuous signal coming into them. Software should be no
> different.
> 
> On Wed, 20 Jul 2011 21:47:23 +0000, "Muranyi, Arpad"
> <Arpad_Muranyi@xxxxxxxxxx> wrote:
>> 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
>> =====================================================================
>> 
>> 
>> 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
>> 
>> 
>> 
>> http://www.teraspeed.com
>> 
>> 
>> 
>> Teraspeed(r) is the registered service mark of
>> 
>> Teraspeed Consulting Group LLC
>> 
>> 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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>> 
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