IBIS Macromodel Task Group Meeting date: 21 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 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 * Bob Ross (Note: Agilent has changed to Keysight) The meeting was led by Arpad Muranyi. ------------------------------------------------------------------------ Opens: - None -------------------------- Call for patent disclosure: - None ------------- Review of ARs: - Todd produce slides for co-optimization requirements discussion next week. - It will take a couple more weeks. - Arpad to review IBIS spec for min max issues. - In progress. ------------- New Discussion: BIRD 128: - Arpad: BIRD 128 is still tabled. BIRD 147.1: - Arpad: SiSoft still is not comfortable with the BIRD. - We are waiting for slides from Todd about industry needs. - Ambrish: We addressed the two question Todd had posed. - Arpad: We need to address industry needs. - SiSoft said the BIRD could not be improved to do this. - Todd: We have tried to resolve discrepancies in the BIRD. - Cadence answered the two questions that were left. - For a while SiSoft had not been certain about whether we would write a new BIRD. - Now we think there should be an alternative BIRD. - It will not come out until the beginning of December. - Arpad: Some people have said BIRD 147.1 is not ready for a vote. - There are issues other than those posed by SiSoft. - Ambrish: We would like to know what the issues are. - Ken: We are 3 years into BIRD 147, it should get a vote. Filter/analog driver (C_comp related): - Arpad: Michael Mirmak made presentations about this. - BIRD 79 is about this. - There are presentations about this. - Arpad show a presentation by Luca Giocotto. - Arpad: This shows non-linear capacitance at high frequencies. - A circuit is proposed. - Tests show good correlation. - It shows what it would look like in IBIS. - Voltage dependence is also modeled. - It adds up to 24 sub-parameters. - The BIRD was rejected in 2003. - David: This is a hard-wired alternative? - Why would EDA vendors support this instead of [External Model] - John: Those replace legacy IBIS, they don't just add to it. - Arpad: It is more challenging to write AMS models. - I have put example models in the public domain. - Walter: IBIS-ISS was created for interconnect. - It would need PWL sources to be enhanced to cover this. - That would be better than AMS. - Arpad: It still would not have event-trigerrable sources. - Walter: IBIS-ISS could have that, and it could be translated. - Receivers are easy. - A driver with C_comp corrected K factor can be done with a SPICE circuit. - It requires a node with time since last translation. - Arpad: It would be easier with a triggered source. - Should we work on adding to IBIS-ISS? - Or should we do something with keywords for the short term? - Randy: We should have done this long ago. - It would be useful for DDR4 and other technologies. - Walter: For DDR4 it is simple. - IBIS-BSS could be used, with an event trigger element. Back-channel proposals: - Walter: We will have a new BIRD, will have vendors review it. - Ken: Will it preclude the back-channel work we have done? - Walter: No. - Todd: The flows are similar but different. - We want the committee to look at the BIRDs side by side. - Ken: Maybe there will then be a third proposal, taking more time. - Todd: We are not confident we have a handle on this yet. - Ambrish: Can we see something next week? - Todd: No, we have to complete it. - Arpad: Voting without an alternative is different than with an alternative. - Ambrish: We have had other proposals. - Arpad: BIRD 147 is the only one for back-channel. - Ambrish: We are concerned about the time. - We have been misled. - Todd: We have tried in good faith to close the gap. New Redriver Flow BIRD: - Walter showed page 8 of Redriver_Flow_BIRD.docx. - Walter: This shows an Init-only flow. - RX2 Init gets the TX2 output into just channel 2. - If TX2 is a redriver then TX1 to RX1 equalization must be added in. - Arpad: Agree with this. - John: Yes, for redrivers but not retimers. - David: It's a fully analog path, not digital. - Walter: Fangyi agrees with this flow. - We are not sure how much difference it makes however. - We had a problem with time domain simulations with an Init-only RX2. - It requires Init_Returns_Impulse along the whole path, plus convolution. - Analyzing all possibilities you end up with 81 combinations. - Handling all of these unique flows would be painful. - The BIRD only handles the case where every model has Init_Returns_Impulse. - Fangyi: Where does it say that? - Walter: It doesn't yet. - IC vendors believe this is the right flow. - Arpad: Can we submit this now, addressing mixed cases later? - This is a flaw in the specification, it should be fixed immediately. - Walter: We could do that. - Fangyi: Retimers are used because they are not linear. - We may not often see Init-only models. - Todd: More than that, they can be adaptive. - Arpad: That might limit the number of possible permutations. - Fangyi: RX1 and TX1 do not both require GetWave. - Only one would be needed, they are part of the same redriver. - There can be optical channels in the middle. - Bob: Is this a flow change? - Walter: It can be more complicated if TX2 equalization depends on channel 2. - Of course the silicon never does that. - A parameter could say the TX is not adaptive. - RX2 can't deal with non-linearities that happen before it if it is Init-only. - Arpad: We should write a BIRD soon to correct this flow problem. AR: Walter write formal Redriver Flow BIRD ------------- IBIS Interconnect SPICE Wish List: 1) Simulator directives