IBIS Macromodel Task Group

Meeting date: 04 April 2017

Members (asterisk for those attending):
ANSYS:                      * Dan Dvorscak
                            * Curtis Clark
Broadcom (Avago):             Xingdong Dai
                            * Bob Miller
Cadence Design Systems:     * Ambrish Varma
                              Brad Brim
                              Kumar Keshavan
                              Ken Willis
eASIC:                        David Banas
                              Marc Kowalski
Ericsson:                     Anders Ekholm
GlobalFoundries:              Steve Parker
IBM                           Luis Armenta
                              Trevor Timpane
Intel:                      * Michael Mirmak
Keysight Technologies:      * Fangyi Rao
                            * Radek Biernacki
                              Ming Yan
Maxim Integrated Products:    Hassan Rafat
Mentor, A Siemens Business:   John Angulo
                            * Arpad Muranyi
Micron Technology:          * Randy Wolff
                              Justin Butterfield
QLogic Corp.:                 James Zhou
                              Andy Joy
SiSoft:                     * Walter Katz
                              Todd Westerhoff
                            * Mike LaBonte
Synopsys:                     Rita Horner
                              Kevin Li
Teraspeed Consulting Group:   Scott McMorrow
Teraspeed Labs:             * Bob Ross
TI:                           Alfred Chong


The meeting was led by Arpad Muranyi.

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Opens:

- Walter noted that he had emailed the ATM a new Redriver Flow presentation and
  a new BIRD 166.1 draft.

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Review of ARs:

- Walter and Radek to work on a draft 4 of BIRD 158.4.
  - Done.  Radek emailed it to ATM list.

- Mike L. to post Radek's Feb 28th BIRD 158 draft as BIRD 158.4 draft 3.
  - Done.

- Mike L. to post draft 2 of Walter's Reference_terminal proposal.
  - Done.

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Call for patent disclosure:

- None.

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Review of Meeting Minutes:

- Arpad: Does anyone have any comments or corrections? [none]
- Walter: Motion to approve the minutes.
- Bob R.: Second.
- Arpad: Anyone opposed? [none]

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New Discussion:

New Redriver Flow BIRD:
- Walter: [sharing his BIRD 166 Redriver Flow presentation]
  - Summary of Issues:
    - Current Statistical Flow for Redrivers (IBIS 6.1):
      - The IR of channel 2 is computed and passed to Tx2's Init().  The output
        of Tx2's Init() is then passed to Rx2's Init().  The output of Rx2's
        Init() is then convolved with the output of Rx1's Init() to get the IR
        that represents the system.  The flaw in this flow is the input to Rx2's 
        Init() should also have contained the upstream channel info (output of
        Rx1) so that Rx2 could optimize itself properly.  The convolution with
        the output of Rx1 should have happened prior to calling Rx2's Init()
        function, not after.
    - Walter's original BIRD 166 proposal:
      - The output of Tx2's Init() is convolved with the output of Rx1's Init(), 
        and the result is passed to Rx2's Init().  The output of Rx2's Init()
        then represents the entire system.  This flow still had issues if the
        Tx2 Init() needed to optimize itself.
    - Walter's new BIRD 166.1 proposal:
      - The IR of channel 2 is convolved with the output of Rx1's Init().  The
        result is then passed to Tx2's Init(), so Tx2 is aware of all the
        channel information it needs to optimize itself.  The output of Tx2's
        Init() is passed to Rx2's Init(), and the output of Rx2's Init()
        represents the system.

- Discussion: Walter noted that currently redriver Tx2s rarely if ever optimize
  themselves.  However, the new flow allowed that possibility and was actually
  simpler than the original BIRD 166 flow.  The new flow meant there was no need 
  for the "Tx_Init_Optimizes" parameter that had been proposed in BIRD166,
  because a Tx2 that optimized itself was handled with the new flow.

  Fangyi noted that this proposed flow was limited to a special case.  It only
  handled pure statistical flow (every device has an AMI_Init() that returns an
  impulse).  Mixtures of GetWave() only models in this flow could fall back to
  the known issues with relying on deconvolution, which doesn't work properly
  with DFE involved.  In addition, even for a pure statistical flow, crosstalk
  could not be handled.  This flow did not produce the IR representing the path
  from Rx1 to Rx2, so crosstalk that coupled into Rx1 could not be properly
  propagated to Rx2.  Walter agreed with Fangyi's statements, and noted that his
  goal with BIRD166.1 was to take a first step and address the existing flow
  error contained in IBIS 6.1 for a pure statistical flow.  Walter noted that he 
  supported Fangyi's proposal for adding additional IRs to the IR matrix passed
  through the Init() functions, and that these enhancements were necessary to
  handle crosstalk and mixed mode (Init() and GetWave() devices) flow.
 
  Ambrish said he thought Walter's BIRD was a first step.  Arpad noted that he
  wanted to ensure that BIRD 166.1 was written in such a way that it was an
  incremental step and would not contain anything that had to be rescinded once
  the enhancements came along.  Radek and Fangyi thought BIRD 166.1 only handled 
  a special case and might conflict with future enhancement proposals.  Walter
  disagreed and thought BIRD 166.1 would address the current flaw in the spec
  and would be a prerequisite for the future enhancements.  Ambrish noted
  that BIRD 166.1 addressed the flow, and future enhancements would change the
  IR matrix but not necessarily the flow.

- Arpad: Are we ready to decide on this today?
  - Do we need to think about it?
  - Can we include BIRD 166.1 in this version of the spec and address Fangyi's
    proposed changes later?
- Walter: I suggest we think about it, discuss it again next week, and then I
          plan to make a motion on whether to recommend BIRD 166.1.
- Bob R.: I agree.  I will have some questions and would like to review Fangyi's 
          proposal to see how it coordinates with BIRD 166.1.

- Mike L.: Motion to adjourn.
- Curtis: Second. 
- Arpad: Thank you all for joining.

AR: Mike L. to post Walter's BIRD 166.1 proposal and presentation.

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Next meeting: 11 April 2017 12:00pm PT
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IBIS Interconnect SPICE Wish List:

1) Simulator directives
