Minutes from the 12 January ibis-atm meeting are attached.
IBIS Macromodel Task Group
Meeting date: 12 January 2021
Members (asterisk for those attending):
Achronix Semiconductor * Hansel Dsilva
ANSYS: * Curtis Clark
* Wei-hsing Huang
Cadence Design Systems: * Ambrish Varma
Ken Willis
Jared James
Google: Zhiping Yang
Intel: * Michael Mirmak
Kinger Cai
Alaeddin Aydiner
Keysight Technologies: * Fangyi Rao
Radek Biernacki
Ming Yan
* Todd Bermensolo
Rui Yang
Luminous Computing David Banas
Marvell Steve Parker
Mentor, A Siemens Business: * Arpad Muranyi
Micron Technology: Randy Wolff
* Justin Butterfield
SAE ITC Jose Godoy
SiSoft (Mathworks): * Walter Katz
Mike LaBonte
Teraspeed Labs: * Bob Ross
Zuken USA: * Lance Wang
The meeting was led by Arpad Muranyi. Curtis Clark took the minutes.
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Opens:
- None.
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Review of ARs:
- Fangyi to add comparisons of proposed variants of Init function input/output
data to his presentation.
- Done. Fangyi to present the new slides today.
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Call for patent disclosure:
- None.
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Review of Meeting Minutes:
Arpad asked for any comments or corrections to the minutes of the January 5th
meeting. Lance moved to approve the minutes. Ambrish seconded the motion.
There were no objections.
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New Discussion:
Redriver Flow Issues:
Fangyi shared his updated presentation "AMI Redriver flow".
Fangyi briefly reviewed slides 3 and 4, unchanged from last week's presentation,
which introduce the terminology he uses (slide 3) and provide a diagram of one
scenario and some of the various crosstalk paths (slide 4).
slide 6 - Comparison of Inputs to AMI Init (new slide)
Note: variant 1 - Fangyi's proposal
variant 2 - Walter's proposal from last week's meeting.
variant 1:
- Tx and Redriver Tx Init Inputs
- IR Matrix columns consist of:
- Direct downstream IR (same as existing flow)
- Cross talk IR terms (same as existing flow)
- Upstream cumulative IR (new column)
- Rx and Redriver Rx Init Inputs
- IR Matrix columns consist of:
- Direct upstream IR (same as existing flow)
- Crosstalk IR terms (same as existing flow)
- Upstream cumulative IR (new column)
variant 2:
- The upstream cumulative IR is the only column of the IR Matrix input to Init
for both Tx and Rx.
slide 7 - Comparison of Outputs of AMI Init (new slide)
variant 1:
- Tx and Redriver Tx Init Outputs
- IR Matrix columns consist of:
- Direct downstream IR equalized (same as existing flow)
- Crosstalk IR terms equalized (same as existing flow)
- Upstream cumulative IR equalized (new column)
- Redriver Rx Init Outputs:
- IR Matrix columns consist of:
- Direct upstream IR equalized (same as existing flow)
- Crosstalk IR terms equalized (same as existing flow)
- Upstream cumulative IR equalized (new column)
- Terminal Rx Init Outputs:
- IR Matrix columns consist of:
- Direct upstream IR equalized (excluding DFE (differs from existing
flow))
- Crosstalk IR terms equalized (excluding DFE (same as existing flow))
- Upstream cumulative IR equalized (AFE and DFE included) (new column)
variant 2:
- Tx and Redriver Tx Init Outputs
- IR Matrix columns consist of:
- Upstream cumulative IR equalized
- IR of the equalization itself
- Redriver Rx Init Outputs:
- IR Matrix columns consist of:
- Upstream cumulative IR equalized
- IR of the equalization itself
- Terminal Rx Init Outputs:
- IR Matrix columns consist of:
- Upstream cumulative IR equalized (equalization includes AFE and DFE)
- IR of the equalization itself (AFE only, no DFE)
Ambrish asked why the first column of the Terminal Rx Init Output in variant 1
does not include DFE (this is how it differs from the existing flow). Fangyi
said we only want DFE applied to the through channel IR, and that is what is
returned in the last column of the Impulse Matrix in variant 1. We want the
direct upstream IR without DFE (column 1) so the EDA tool can calculate the
contributions from all of the various crosstalk paths.
slide 8 - Post processing steps (new slide)
This slide enumerates various post processing steps the EDA tool will have to
do in the case of variant 2 to compute all the quantities that the model returns
in the case of variant 1. Walter noted that, at first glance, he thought the
steps listed for variant 2 might be double counting the upstream channel, but he
needed to review them more carefully.
slide 9 - comparison of the capabilities of the two variants (new slide)
Fangyi noted that two things variant 1 supported that variant 2 didn't support
were a Tx Init optimizing based on the downstream IR or any Init optimizing
based on crosstalk terms.
Walter mentioned that one other feature of variant 1 is that it provides some IP
protection by not directly returning the equalization IR, but he wondered if
the IP vendors thoughts this was a real benefit. He noted that one advantage of
variant 2 is that it lets the EDA tool create a proxy GetWave for an Init-only
model by using the IR of the equalization itself, which is returned by Init in
variant 2. Arpad suggested this be added to the comparison table. Fangyi added
a new row to the table "Allows EDA tool to construct GetWave (without DFE) for
the model based on the Init output?" (variant 1 - no, variant 2 - yes).
The comparison table indicates both variants support the GetWave flow and even
support the case of models with a GetWave that depends on the input to Init, as
long as "all models are Dual". Arpad noted Walter's previous statements that
Init-only models were okay upstream, but every model downstream of the first
model with a GetWave had to have a GetWave. Fangyi agreed with this statement,
but said he wanted to avoid the complicated language and instead had gone with
the simpler "all models are Dual".
While reviewing the pros and cons, Walter and Fangyi came up with a hybrid of
the two variants. This hybrid approach could be controlled by two new
independent Reserved Parameters. One parameter (true/false) as Usage In would
be used to select, or as Usage Info would indicate, whether the model takes an
additional column in the IR matrix containing the cumulative upstream IR
(variant 1). A second parameter (true/false) as Usage In would be used to
select, or as Usage Info would indicate, whether the model returns an additional
column at the end of the IR matrix containing the IR of the equalization itself
(without DFE). If both parameters are true, the model provides the benefits of
both variants, but the parameters could be used independently. If both
parameters are false or don't exist, then the model supports the legacy flow.
Fangyi took an AR to update the new comparison slides with information for this
hybrid approach. Walter asked that we make sure to note that the Terminal Rx
model need not be Dual, as it is reasonable to have a terminal Rx that does not
want to return an IR from Init because it wouldn't include the DFE effects.
Ambrish asked that we add a line noting that if all of the models are GetWave-
only, then none of this is a problem.
Arpad asked if we should start on a BIRD or wait until we see Fangyi's new
slides next week. Fangyi suggested waiting until next week.
Note: At last week's meeting Arpad suggested we hold off on posting the
presentation slides and post them after Fangyi had added the comparison info.
We will again hold off on posting and wait for next week when Fangyi has added
the new hybrid variant information.
- Ambrish: Motion to adjourn.
- Walter: Second.
- Arpad: Thank you all for joining.
AR: Fangyi to add information on the new hybrid variant to his presentation.
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Next meeting: 19 January 2021 12:00pm PT
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IBIS Interconnect SPICE Wish List:
1) Simulator directives
