IBIS Macromodel Task Group

Meeting date: 28 October 2014

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

(Note: Agilent has changed to Keysight)

The meeting was led by Arpad Muranyi.

------------------------------------------------------------------------
Opens:

- Todd: I have a TX Dj topic to discuss.

--------------------------
Call for patent disclosure:

- None

-------------
Review of ARs:

- Walter write formal Redriver Flow BIRD.
  - Walter: The introduction has been written.
    - Would like to have Fangyi present for discussion.
    - It has been emailed only, not posted.
    - This has not been submitted yet.

AR: Walter send Redriver Flow BIRD to Mike for posting.

- Todd produce slides for co-optimization requirements discussion next week.
  - In progress.

- Arpad to review IBIS spec for min max issues.
  - In progress.


-------------
New Discussion:

Introduction of Steve Parker:
- Looking at IBIS-AMI models.
- Previously spent a lot of time with DDR, returning to HS SerDes modeling.


TX Dj:

- Todd: People are challenging the way TX Dj is specified.
  - Some people would like to see a profile other than flat distribution for TX Dj.
  - Deterministic jitter is by definition pattern dependent.
  - The spec is at odds with that, TX Dj does not consider pattern.
  - Vendors would like to see it defined some other way.
- Arpad: Should this be on future agendas?
- Todd: We are not ready to write anything.
  - Trying to see if others have the same issue.
- Arpad: I have seen some problems in this area.
  - We probably need to improve it somehow.
- Walter: If Keysight and Cadence can look into this we can schedule a discussion.
  - There should be an AR.

AR: Mentor, Keysight, Cadence investigate TX Dj issues.


C_comp improvements:

- Arpad: I have nothing new on this, am seeking feedback.
- Walter: IBIS assumes Pullup+Pulldown+C_comp structures.
  - C_comp is not a good representation of DDR3 and DDR4 buffers
  - It's not good for some SerDes either.
  - A sub-circuit description would be good for receiver.
  - Drivers have to match an output profile that assumes a certain C_comp circuit.
  - They are non-linear.
  - If we limit this to receivers it's pretty simple.
  - That could be done with IBIS-ISS.
- Arpad: We might have a solution for receivers now.
  - A linear IBIS-ISS subckt could be written now.

- Walter: The ESD protection circuit complicate this.
- Randy: DDR3 and DDR4 terminations see small voltage swings, the diodes don't turn on.
- Walter: So linear circuits are OK for receivers.
  - How about drivers?
- Randy: That is a more complex problem.

- Arpad: How big is the need for drivers?
  - It only matters for reflections.
- Randy: Drivers in stacked packages can have local reflections.

- Walter: How much error might there be for EDA tools compensating for C_comp?
- Radek: It's not really different from compensating for a package.
- Walter: The Final Stage Subckt proposal might apply then.
  - I wrote a BIRD some time ago but never submitted it.

AR: Walter send BIRD on C_comp enhancements.


BIRD 147.1:
- Arpad: We are waiting for a new proposal from SiSoft.
  - Can we vote on BIRD 14.1?
  - Some have said it needs some fixes.
- Walter: Cadence can untable it in the Open Forum any time.
- Arpad: They expect us to make a recommendation.
- Radek: I have given my comments about training.
- Ambrish: Please send your comments to me.
- Arpad: We should get Bob's feedback too.
- Mike: It is not unheard of for subcommittees to return proposals without recommendation.
- Arpad: We should make sure Ambrish has all feedback before deciding.

AR: Ambrish ask Bob for written feedback on BIRD 147.1


-------------
IBIS Interconnect SPICE Wish List:

1) Simulator directives