[ibis] Re: BIRD175.2: Extending IBIS-AMI for PAM4 Analysis

From: Ed Sayre <esayre@xxxxxxxx>
To: Lance Wang <lwang@xxxxxxxxxx>, "twesterh@xxxxxxxxxx" <twesterh@xxxxxxxxxx>, "bob@xxxxxxxxxxxxxxxxx" <bob@xxxxxxxxxxxxxxxxx>, "ibis@xxxxxxxxxxxxx" <ibis@xxxxxxxxxxxxx>
Date: Wed, 10 Jun 2015 16:03:53 +0000

Dear IBIS Colleagues:

I am very concerned by the implications of Lance's email. It says that there
have been purposeful misleading activities going on in the IBIS space. These
activities muist stop before we approach "fixing" the problems.

I was the first Chairman of the IBIS Users' Group and during that experience, I
would have been very upset if such mis-leading activities were going on. Use
of "non-standard" features have no place in a "standard". If such features are
used, they must be clearly identified as such and provision for "shutting them
off" should be clearly stated.

Our industry has prospered because of the use of clear communications in
standards. Any perversion of tool features is like selling a breakable hammer
ot a blunt knife. Maintaining integrity is a clearly the first duty of any
tool vendor or modeler.

I feel that the absebce of a User's Guide is a severe deficiency.

Sincerely,

Ed Sayre
Teraspeed Consulting - a Division of Samtec, Inc.

From: Lance Wang [mailto:lwang@xxxxxxxxxx]
Sent: Wednesday, June 10, 2015 10:56 AM
To: twesterh@xxxxxxxxxx; Ed Sayre; bob@xxxxxxxxxxxxxxxxx; ibis@xxxxxxxxxxxxx
Subject: Re: [ibis] Re: BIRD175.2: Extending IBIS-AMI for PAM4 Analysis

Well said, Todd.

I do think the root cause of this frustration is because the "particular" model
only works (or works as expected) in the "particular" tool(s). Sometimes, It
even had been modeled on purposely and using the word "IBIS" to fool the users.
It may be passed thru the IBIS golden parser (e.g. Putting special keywords in
the commented line, in the executables, in the external models, etc.). This is
not only happened for IBIS-AMI models but also for the traditional IBIS models.

They are not IBIS Compliant. So, they are not the Standard IBIS models. Please
remember that the inter-operability feature is the most important feature for
any Standards as well as IBIS.

Here are my suggestions as the extension of Todd's comments:

1. For the users, we should stop using the non-standard models. If it is so
called IBIS/IBIS-AMI model, it should be IBIS Standard Compliant.
2. The model vendors/EDA vendors, let's stop to make the "fooled-IBIS"
models. We can have our own model format. But don't call it is IBIS model or
"IBIS something" to fool the users
3. IBIS Open Forum should come out a detailed validation flow in order to
stop non-IBIS Compliant models
4. Finally, I would echo Todd's #2 comment again. Let's work with IBIS Open
Forum for identifying and resolving the weakness in the spec. IBIS Open Forum
welcomes any comments, suggestions and solutions to make IBIS more robust. But
not another way around.

Best regards,

Lance Wang
IO Methodology Inc.
978-764-2298

On 6/10/15, 9:35 AM, "Todd Westerhoff"
<twesterh@xxxxxxxxxx<mailto:twesterh@xxxxxxxxxx>> wrote:

Ed,

That's a pretty broad topic. I have no doubt that your customers are
experiencing issues; it's been our experience that different model makers and
EDA vendors are interpreting key sections of the IBIS-AMI spec differently, and
that is affecting how models run and the results they produce.

In our opinion, there are two parallel paths to solving this problem:

1) Work directly with model makers to understand why a *particular* model
doesn't work in a *particular* tool. In other words, the details matter.

2) Identify and resolve weaknesses in the spec that affect model
robustness and portability - particularly areas where a model/tool can produce
different results and *still* conform to the spec (I like to call this
condition under-specified)

As you would expect, we do both. Obviously, we focus our efforts on the EDA
tool we have access to (ours) and seek to bring our learnings back to the IBIS
committee.

Bottom line, there's no easy answer to your question - if you're in a position
to help us create examples and guides, we'll take all the help we can get!

Todd.

Todd Westerhoff
VP, Semiconductor Relations
Signal Integrity Software Inc. * www.sisoft.com
6 Clock Tower Place * Suite 250 * Maynard, MA 01754
(978) 461-0449<978-461-0449> x24 * twesterh@xxxxxxxxxx
"I want to live like that"
-Sidewalk Prophets

From: ibis-bounce@xxxxxxxxxxxxx<mailto:ibis-bounce@xxxxxxxxxxxxx>
[mailto:ibis-bounce@xxxxxxxxxxxxx] On Behalf Of Ed Sayre
Sent: Tuesday, June 9, 2015 5:25 PM
To: bob@xxxxxxxxxxxxxxxxx<mailto:bob@xxxxxxxxxxxxxxxxx>;
ibis@xxxxxxxxxxxxx<mailto:ibis@xxxxxxxxxxxxx>
Subject: [ibis] Re: BIRD175.2: Extending IBIS-AMI for PAM4 Analysis

Bob:

A number of folks that I communicate with have expressed great frustration with
the use of IBIS-AMI models in their simulators of choice. Are there examples
and a user guide which go beyond the specification?

ed

From: ibis-bounce@xxxxxxxxxxxxx<mailto:ibis-bounce@xxxxxxxxxxxxx>
[mailto:ibis-bounce@xxxxxxxxxxxxx] On Behalf Of Bob Ross
Sent: Tuesday, June 09, 2015 11:39 AM
To: ibis@xxxxxxxxxxxxx<mailto:ibis@xxxxxxxxxxxxx>
Subject: [ibis] Re: BIRD175.2: Extending IBIS-AMI for PAM4 Analysis

All,

On re-reading BIRD175.2, I have a few comments:

1. Both "PAM4_UpperThreshold" and "PAM4_Upper_Threshold" appear in BIRD175.2.
(Same for *Center_Threshold and *Lower_Threshold.)

I would prefer using the underbar "_" for these parameters and also for
the *Offset parameters.

2. For the *Threshold parameters, the rule:

* If the Reserved AMI Parameter Modulation is set to "PAM4" and these
threshold values are not declared, the model maker shall assume that the EDA
tool may choose a value for each of these three parameters.
should be changed.

All three parameters definitions should be declared if Modulation is set to
"PAM4" with Value
or in a List. Otherwise we are using "implicit" parameter definitions in
IBIS-AMI on unpredictable
results between EDA tools. However, the EDA tool can re-assign the values.

3. The defaults of 0.0 are OK for the *Offset* parameters, if they are missing.

(I will be out today, so I may not be able to respond.)

Bob

From: ibis-bounce@xxxxxxxxxxxxx<mailto:ibis-bounce@xxxxxxxxxxxxx>
[mailto:ibis-bounce@xxxxxxxxxxxxx] On Behalf Of Mirmak, Michael
Sent: Friday, June 05, 2015 11:34 AM
To: ibis@xxxxxxxxxxxxx<mailto:ibis@xxxxxxxxxxxxx>
Subject: [ibis] BIRD175.2: Extending IBIS-AMI for PAM4 Analysis

An updated BIRD175.2, Extending IBIS-AMI for PAM4 Analysis, has been submitted
on behalf of Walter Katz, Mike Steinberger, and Todd Westerhoff of SiSoft;
Fangyi Rao of Keysight Technologies; Bob Miller of Avago Technologies; and
Hongtao Zhang of Xilinx. It will be discussed at the next IBIS Open Forum
teleconference.

The text of the BIRD can be viewed at
http://www.eda.org/ibis/birds/bird175.2.docx.

Michael Mirmak
Intel Corp.
Chair, IBIS Open Forum
http://www.eda.org/ibis/

References:
- [ibis] Re: BIRD175.2: Extending IBIS-AMI for PAM4 Analysis
  - From: Lance Wang

[ibis] Re: BIRD175.2: Extending IBIS-AMI for PAM4 Analysis

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