DATE: 12/10/98
SUBJECT: 12/7/98 EIA IBIS Summit Meeting Minutes
VOTING MEMBERS AND 1998 PARTICIPANTS LIST:
AMP (Martin Freedman)
Applied Simulation Technology Norio Matsui, Raj Raghuram*
Cadence Design (& UniCAD) C. Kumar, Don Telian, Patrick Riffault,
Craig Lewis, Greg Fitzgerald, Paul Galloway,
Patrick Dos Santos, Catherine Weiss,
Alain Tribaudot, Geoffrey Ellis,
Todd Westerhoff, Ken Willis, Mike LaBonte
Cisco Systems Syed Huq*, Sergio Camerlo, Irfan Elahi
Compaq Shariq Rahma, Jeff Chu, Bob Haller,
(Digital Equipment Corp.) Doug Burns, Steve Coe
Cypress Bruce Wenniger*
H.A.S. Electronics Haruny Said
Hewlett Packard (EEsof, etc.) Karl Kachigan, Henry Wu, Paul Gregory,
Brenda Arena, Hans Wiggers*
High Design Technology Razvan Ene
HyperLynx Kellee Crisafulli, Matthew Flora, Gene Garat,
Dave Kohlmeier
Incases Olaf Rethmeier, Scott Jacobson,
Werner Rissiek
Intel Corporation Stephen Peters, Arpad Muranyi, Frank Kern,
(& formerly NCR) Will Hobbs, Prakash Radhakrishnan,
Mohammed Hawana, Martin Chang, Dave Moxley,
Tim Schreyer, Lyndell Asbenson
LSI Logic (Symbios Logic) Larry Barnes
Mentor Graphics (Zeelan, Bob Ross*, George Opsahl, Mark Noneman,
Interconnectix, etc.) Tom Dagostino*, Karine Loudet, Jean Oudinot,
Manuel De Almeida, Stephane Rousseau,
Neven Orhanovic, Mohamed Mahmoud, Kevin Cohan
Mitsubishi Tam Cao
Motorola (Ron Werner)
National Semiconductor Cheng-Yang Kao, John Goldie, Ikchang Song,
Milt Schwartz*
North East Systems Associates Edward Sayre, Kathy Breda, Michael Baxter,
(NESA) Jon Green, Jinhua Chen
NEC (Hiroshi Matsumoto)
Quantic EMC (Mike Ventham)
Texas Instruments Thomas Fisher, Harvey Stiegler,
Vincent Chang, Jean-Claude Perrin,
Peter Forstner
Thomson-CSF Jean-Marc Claveau, Laurent Duzaic,
Saverio Lerose, Benoit Meyniel,
Jean Lefebvre
Viewlogic Jon Powell, Chris Rokusek*, Guy de Burgh,
Gary Mandel
VeriBest Ian Dodd, David Weins, Ian Gabbitas
VLSI Technology D.C. Sessions*, Derwin Mattos*
Zuken-Redac (John Berrie)
OTHER PARTICIPANTS IN 1998:
3Com Steve Miller
3Dfx Interactive Ken Wu
A.T.Sinker Tony Sinker
Actel Eric Tardif, Emmonvelle Gaudin
Aerospatiale Lionel Dreux, Claude Huet
Alcatel (Bell, Espace, etc.) John Fitzpatrick, W. Temmerman,
Laure Bessettes, Jean-Claude Pourtau,
Daniel Peron
ALS Design Yves Mouquet
Ansoft Eric Bogatin
Apple Fred Floresca, Danny Itani
Apteq Design Systems Dan FitzPatrick
Atmel Ali Baktashian
Avanti Nik Bannov
CERN Olivier Clere, Jean-Michel Sainson,
Rudi Zurbroken
Corning John Nieznanski
Crucial Technology Rathna Reddy
DIVA Corp Tieng Nguyen
Dynamic Research Corporation Mike Walsh
EIA Patti Rusher
EMC Fawn Engelmann, Fabrizio Zanella
ENST, Paris Jean-Jacques Charlot
European CAD Standardization Adam Morawiec
Intitiative (ECSI)
Fairchild Semiconductor Peter LaFlamme
Focus Technology John Salzillo, Gary Brophy, Mike Arieta,
Jim Skane
Hyundai Farhad Tabrizi*
IBM Richard Steinle, Kevin Jackson, Greg Edlund,
Douglas Stout*
InRange Elliot Lipin
Intracon Design Ltd. Derek Laidlaw
LG Semicon America Michael Spooer*, Seung-Tae Lee*
Micron Technology Terry Lee*
Molex Gus Panella
Philips Semiconductor Todd Andersen
Rockwell Semiconductor Tim Gilbert
Scottish Electronics Robert Easson
Manufacturing Center (SEMC)
Seagate Vanessa Howard
Signal Integrity Software Barry Katz
SGS-Thomson Philippe Lefevre
Siemens Gerald Bannert, Bernhard Unger,
Christian Marot, Miguel Hernandez,
Gil Russell, Hartmud Terletzki*
SSEI Tom Hawkins
Stratus Bruce Heilbrunn, Steve Mango, Lewis Steiner,
Karla Eignor, Rich Newell
Summit Computer Systems Bob Davis
Sun Microsystems Lam Dong, Kevin Ko, Tay Ansari, Ken Weiss,
Derek Tsai*
Symmetry Andy Hughes
Tektronix Nassrin Ghahyasi, Tom Brinkoetter,
Brad Weber, John Rettig
Teradyne Michael Khusid
Time Domain Analysis Systems Dima Smolyansky
Transmeta Bill Gervasi*
TranSwitch Bill Todd
TRILOGIC Joe Socha
Ultratest International Chris O'Connor
Xilinx Susan Wu, Rob Eccles*
In the list above, attendees at the meeting are indicated by *. Principal
members or other active members who have not attended are in parentheses.
Participants who no longer are in the organization are in square brackets.
Upcoming Meetings: The bridge numbers for future IBIS teleconferences are
as follows:
Date Bridge Number Reservation # Passcode
December 18, 1998 (916) 356-9200 3-241993 1195347
All meetings are 8:00 AM to 9:55 AM Pacific Time. We try to have agendas
out 7 days before each Open Forum and meeting minutes out within 7 days
after. When you call into the meeting, ask for the IBIS Open Forum hosted
by Will Hobbs and give the reservation number and passcode.
NOTE: "AR" = Action Required.
-------------------------------- MINUTES -----------------------------------
IBIS SUMMIT MEETING
The IBIS Summit Meeting was held at the Shelter Pointe Hotel and Marina in
San Diego, California at the same time as the JEDEC JC-40 and JC-16 meetings.
About 19 people representing 16 organizations participated in the meeting.
The food, refreshments, and the facilities were excellent. The Minutes here
just briefly note some of the content of the meeting and some discussion.
Some of the presentations and related documents will be uploaded at:
http://www.eda.org/pub/ibis/summits/dec98
INTRODUCTIONS AND BUSINESS
- Bob Ross (Mentor Graphics)
After a delicious buffet lunch for attendees, Bob Ross opened the IBIS meeting
by having the participants introduce themselves. There appeared to be equal
representation from the IBIS and JEDEC communities. The semiconductor sector
was more heavily represented than the user and EDA tool vendor sectors.
An underlying theme of this meeting was to introduce and discuss possible new
modeling requirements and needs. Following this theme, the EIAJ activity on
I/O Interface Model for Integrated Circuits (IMIC) would be discussed because
it had some possible ideas to deal with details that might not be currently
handled well in IBIS.
Bob noted that due to the last minute introduction of BIRD57 on Timed Bus Hold
Extension, we are deferring the vote on IBIS Version 3.2 that had been
scheduled for Friday, December 18, 1998 to the following meeting scheduled on
Friday, January 15, 1999. That will give us time to review in the December
18, 1998 meeting the pending BIRD56 and BIRD57, initiate possible ibischk3
changes, and prepare IBIS Version 3.2 for voting with these BIRDs included.
Bob also summarized that the next IBIS Summit Meeting is scheduled on Monday,
February 1, 1998 at DesignCon99 in San Jose. The EIA IBIS Open Forum is an
Associate Sponsor of DesignCon99 allowing DesignCon99 to provide the meeting
facilities and refreshments. National Semiconductor will sponsor the
luncheon. In the past, National had sponsored the whole meeting including
facilities. Milt Schwartz will be the contact person for signing up meeting
participants and signing up and gathering presentations. A first notice
should be issued this week. The focus of that meeting will be on Accuracy
issues and future IBIS features. Also, through the Associate Sponsorship
arrangement, there will be an IBIS booth on the Exhibition floor that will
provide IBIS information and demonstrate the IBIS User's Group accuracy test
board measurements. Jon Powell is the contact person for the booth.
Ad Hoc presentations and discussion topics were solicited:
Active Terminations - Derek Tsai
Bus Switches Functionality - Tom Dagostino
Accuracy Testing of Measurement Based Models - Tom Dagostino
JEDEC JC-16.2 IBIS Presentation - Bob Ross
PROGRAM NOTES FOLLOW (Scheduled and Ad Hoc Presentations):
INPUT THRESHOLD MODELING
- D.C. Sessions (VLSI Logic)
D.C. Sessions noted that as a result of tighter timing margins, the old input
threshold limits such as Vinh = 2.0 V and Vinl = 0.8 V are becoming too
conservative to be practical. Input signals can easily have a ledge in the
in the region between Vinh and Vinl. The actual thresholds are much tighter.
Also JEDEC JC-16.2 is standardizing on closer threshold limits for newer
technologies.
D.C. noted that for many technologies, the Input thresholds were related to
the power supply voltage. So D.C. suggested a linear adjustment factor that
is related to the rail to determine more accurate thresholds. Bob Ross
mentioned that this might already exist indirectly using the [Model Spec]
keyword.
D.C. also noted that the timing delay was a function of how much the input
signal went over the first threshold. D.C. showed some time shifted responses
as a function of threshold overvoltage from 25 mV to about 1.6 V. The delays
shrank from about 3 ns to 300 ps. For this particular simulation, D.C.
fit the data to a 2/3rds power relationship:
t = to + K/(Vin - Vth)**(2/3)
D.C. suggested a timing table could be proposed for IBIS to capture this
input resolution.
To summarize, D.C. presented the following draft proposal:
1) Threshold Voltage
"Add a first-order term to the exiting Vin specs. DC trip point is defined as
the specified value at the specified supply voltage plus (the new value) times
the difference in supply voltage. Alternately, add a table. In effect, turn
the current and scaler values into lists."
2) Timing
"In keeping with IBIS's preferred use of observable properties, add an
[input_delay] table giving relative delay for input voltages relative to the
specified thresholds. Thus, if Vinl is 800 mV under some condition, the table
entry at 200 mV is the added delay for signals at 1000 mV. Simulator
providers would be free to innovate with respect to dynamic algorithms for
complex input waveforms.
OVERVIEW OF JEDEC JC-16 ACTIVITIES
- Hans Wiggers (Hewlett-Packard and Chair. of JC-16)
Hans Wiggers introduced himself as Chair of the JC-16 group under which there
are two subgroups. The group is involved with interface topologies. They
also provide an educational function.
Hans commented that the threshold and input characteristics are of interest.
Also a driver specification consisting of a Max and Min IBIS style table
for bounding values is a current proposal under discussion for memory
devices.
Hans listed a number of standards that the group has been involved with.
Low Performance standards include: TTL, LVTTL, LVCMOS, 2.5 V non-terminated
CMOS, 1.5 V interfaces. High performance standards include: GTL, Center
Tap Terminated, (High Speed Transmission Logic) HSTL -1, -2, -3, -4, (Series
Stub Terminated Line) STTL for 3.3 V, now 2.5 V and future 1.5 V.
The best inputs are with a terminator to Vtt = Vddq/2 (the quiescent Vdd
voltage). Hans showed some network topologies to illustrate this.
One distinction is that JEDEC standardizes parameters that can be put in data
sheets. Data sheet information is contractual; customers can reject the
components if they do not meet the data sheet specifications. So there is
a reluctance for very tight parameters which may be hard to test against.
The immediate future activities of JEDEC JC-16 are modifying STTL-2, adding
IBIS-like tables to driver specifications, and specifying LVCMOS for 1.5 V.
ACTIVE TERMINATIONS (Ad Hoc)
- Derek Tsai (Sun Microsystems)
Derek Tsai showed a device/net topology with a switchable termination and
asked whether IBIS Version 3.1 could cover it. The topology involved a
pullup termination Rup that was active only in the driving mode. Rup and Rdn
source and load terminations were equal to Zo and were switchable from up
to down states. It appeared that Rup was disabled only in the receiver mode.
Derek listed some characteristics:
1. Back-to-back switching
2. Rup acts as termination (active) and never turns off until it needs
to drive "low"
3. Rdn drive '0'
4. Fall: Rup -> Rdn
Rdn -> Rup and stays on
5. Problems: 1) transition has glitches, 2) bus contention
(under work-around simulations)
There was some discussion and clarification. Bob Ross indicated that pending
IBIS Version 3.2 had submodel parameters both for dynamic clamps and for bus
hold style circuits. While Bob thought that the bus hold extensions
documented in pending IBIS Version 3.2 would model Derek's circuit,
discussions during a break revealed that perhaps the dynamic clamp in the
static mode was the appropriate representation.
SERIES SWITCH EXTENSION (Ad Hoc)
- Tom Dagostino (Mentor Graphics)
Tom Dagostino drew a topology showing nets containing series switches that
were turned on and off to control the connection paths. Tom asked if the
turning on and off characteristics of the on/off and off/on transitions of
the switch itself were important to model. Several people responded that they
needed to model such effects. The series switch extension in IBIS Version 3.1
models only the static on or static off impedances in the path itself, but not
the transition characteristics.
IMIC DISCUSSION
- Bob Ross (Mentor Graphics)
Bob Ross introduced the background of why we are discussing the IMIC activity
at this meeting. Bob indicated that the IBIS Committee people had been
following the IMIC activity since February, 1997 through October, 1998 as a
result of several private meetings and several IBIS Summit presentations
on IMIC. At the London IEC meeting in September, 1998, the request was made
that the IBIS committee work with the I/O Modeling Project group responsible
for IMIC since the activities appeared to overlap. Bob indicated that there
were subsequent meetings with Dr. Hideki Fukuda in October, 1998 on this
subject and that the topic was appropriate at this meeting since it related
to potential IBIS future extensions.
As an introduction, the IMIC activity had begun in 1996 to extend IBIS
Version 2.1. The intent was to create extensions to deal with signal
integrity, power integrity (ground and power bounce and SSO simulations), and
EMI simulations. Also, the extension was needed to deal with emerging
buffer topologies. Bob noted that IBIS also expanded its capability leading
to IBIS Version 3.X extensions. However, there could be limitations to the
IBIS behavioral approach that could be solved by IMIC and SPICE approaches.
Bob summarized the IMIC approach both in his presentation and copies of
slides provided by Fukuda-san. IMIC formats Modules (similar to IBIS EBD),
ICs (Similar to IBIS Components and Models), and Packages (similar to IBIS
Packages). However, IMIC supports a SPICE netlist syntax plus some IBIS
wrapper keywords. IMIC also introduces a table SPICE representation of
MOSFET, Diode and Bipolar devices that allows process information to remain
proprietary. The models can be complex as shown by 1D (corresponding to IBIS,
2D and 3D samples. However, there could be efficiencies associated with
scaling the buffers rather than providing different models for each physical
geometry variation.
Bob noted that IMIC does not include some specification and informational
details contained in the IBIS format that are used by many simulators used for
digital circuit board design and analysis. Such information includes model
type (e.g., Input, Output, I/O, etc.), threshold specifications, timing test
loads, and some connection information documenting differential I/O pin
connections, power rail pin connections, etc.
Bob outlined some IBIS/IMIC approaches:
Merge IBIS and IMIC
Link from IBIS to IMIC features of interest
Keep IBIS and IMIC separate, but provide IMIC to IBIS translation paths
There are practical and business advantages and disadvantages to each of these
approaches. The most interesting is to explore Linkage to the package
extensions and to the buffer formulations. These also relate to possible
SPICE linkages and to both Table Spice and BSIM Version 3.2.2 extensions
being standardized by the Compact Modeling Council. Bob noted one novel
feature of the IMIC format is that it might be possible to format typical,
minimum and maximum package characteristics in the same document. Bob was
interested in accuracy validation of the table SPICE approach, and this
is a subject in the next presentation.
An IBIS committee study group consists of Stephen Peters, Raj Raghuram, Norio
Matsui, and Bob Ross. Others are welcome to join. The EIAJ group will also
have a small group for interaction.
In the subsequent discussion, Syed Huq pointed out the IMIC is not an
officially approved standard - it is still in draft mode and has not gone
through official acceptance processes. In contrast, IBIS is an approved
ANSI/EIA standard.
VALIDATION OF EIAJ IMIC MODELS
- Raj Raghuram (Applied Simulation Technology)
Raj Raghuram also presented an overview of IMIC using selected copies of older
presentations. The multi-dimension table format is an extension of Berkeley
SPICE. The approach is supported by several commercial SPICE simulators, and
the tables can be automatically generated by 3D DC sweeps and selecting the
options to print capacitances at each point. With generic SPICE, more
analysis work is needed by doing AC analysis at each operation point to
extract capacitances.
The validation process was to generate a Table SPICE model from a driver
SPICE model, and then compare the simulation results of each under the
same set of test loads.
Example 1 used the Motorola 74LCX245 low voltage CMOS Octal transceiver
model as the basis. Simulations were done with these driving parameters:
1 ns Tr, 1 ns delay, 9 ns pulse width. The results were compared with
these test circuit loads: 500 ohms and 5 pF to ground, 50 ohms to ground,
50 ohms to Vcc (3 V), and 500 ohms terminating a 50 ohm and 1 ns transmission
line. All of the results showed very similar waveform shapes when overlayed.
There was a slight delay mismatch, but Raj considered that a problem based
on low Table SPICE resolution. He did not have time to investigate and
provide refinements to this skew in results or to investigate the effects of
3D to 2D model simplifications.
Example 2 compared a Texas Instruments CBT16233 with a Table SPICE
formulation. The device was loaded with a 1 kiloohm and 5 pF at the end of a
65 ohm and 1 nS transmission line. Excellent, overlaying response was shown
between the orignal SPICE model simulation and table SPICE models generated
from Applied Simulation Technology and HSPICE simulators.
Raj concluded that the correlation was good and that the IMIc model is a
viable SPICE-like alternative that protects proprietary process information.
ACCURACY TESTING OF MEASUREMENT BASED MODELS
- Tom Dagostino (Mentor Graphics)
Tom Dagostino raised the question and led the discussion on what is needed to
test the accuracy of measurement based models. A number of points were made
relating to accuracy and to what should be included in a measurement based
model are captured here.
One point is that measurement based models document actual characteristics
of the device. However, since it was not known whether that device was
really typical, the scaling of the device data for min and max characteristics
should be left to the simulator tool. It should not be given in the model.
D.C. Sessions was interested in a range for different processes.
Tom indicated that measurements could be done on a number of devices from
the same vendor for different lots over time to get a statistical spread.
Milt Schwartz and others indicated that sometimes the fabrication lab does
not have the process skew information. Furthermore, there is a reluctance
to provide too tight of information which will result in being forced to
guarantee tighter information in the data sheet. So the documentation of
lots was becoming less rigorous.
Tom asked if it were valid to test different devices from a same technology
from the same vendor, and several people stated that this was not valid since
even with what is documented as the same family, the actual devices may have
different characteristics and come from different processes or die sizes. So
it was not a defendable practice to infer that different characteristics were
related to min and max variations.
Regarding test and extraction conditions, Chris Rokusek and other people
stressed that capturing the information based on the IBIS Cookbook conditions
of 50 ohms to ground and to Vcc and testing against those conditions was a
preferred approach. There might be some exceptions, but even if the voltage
swing is not full scale, the model was still tuned to the actual transmission
line connections that need to be simulated. Other test loads could be
included in the IBIS model for the purposes of validating the model, although
few people are doing this. Examples of a validation load are connection of
50 ohms to Vcc/2 and using some capacitive loads.
D.C. Sessions commented that he expected that the contributions of process
variation, temperature variations (over a 0 degrees C to 125 degrees C) and
a 10 percent voltage variation to have about equal contribution effects.
So if IBIS models are extracted from measurements under simultaneous voltage
and temperature variations, it might be defendable to infer the process
variation effect by some additional scaling by 1/2.
Chris indicated classified accurate models as
Level 0: ramp based
Level 1: one waveform based (one rising, one falling)
Level 2: two waveform based (two rising, two falling)
Chris felt that the Level 0 and Level 1 models were of comparable accuracy,
and Level 2 models provide a great improvement. D.C. pointed out that the
two waveform extraction provided both the turn on and turn off characteristics
needed for the complete characterization. Chis noted that the 50 ohm load
provided a better load line for actual operating conditions. D.C. mentioned
that the 50 ohm extraction took into account the buffer Miller capacitance
that affects the response.
IBIS PRESENTATION AT THE JEDEC JC-16 MEETING (Ad Hoc)
- Bob Ross (Mentor Graphics)
Bob Ross indicated that Stephen Peters had been scheduled to do a presentation
both at the IBIS Summit Meeting and also at the JEDEC JC-16 meeting, but he
was unable to attend. So we needed to draft a presentation for the next day
JEDEC meeting. D.C. Sessions provided some general guidelines, and the action
was to work out presentation details at a dinner gathering with those people
who would attend the JEDEC meeting.
(Bob Ross and Chris Rokusek created a mostly hand-drawn IBIS Overview and
Simulation presentation for the JEDEC Meeting on Tuesday, December 8, 1998.
Several other IBIS committee participants attended. The presentation
appeared to be well-received and prompted several questions. As an action
item D.C. Session was asked to chair a JEDEC JC- 42 and JC-16 Task Group on
Formation of IBIS Models. Initially people from Hewlett-Packard, IBM, Xilinx,
Western Digital, United Memories, Micron, and Samsung joined this Task Group.
Participation is also open to IBIS Committee participants. Contact D.C.
Sessions to join.)
NEXT MEETING:
The next teleconference meeting will be on Friday, December 18, 1998 from
8:00 AM to 10:00 AM. BIRD56 and BIRD57 are scheduled for votes.
==============================================================================
NOTES
IBIS CHAIR: Bob Ross (503) 685-0732, Fax (503) 685-4897
bob_ross@mentorg.com
Modeling Engineer, Interconnectix BU of Mentor Graphics
8005 S.W. Boeckman Road, Wilsonville, OR 97070
VICE CHAIR: Stephen Peters (503) 264-4108, Fax: (503) 264-4515
sjpeters@ichips.intel.com
Senior Hardware Engineer, Intel Corporation
M/S JF1-56
2111 NE 25th Ave.
Hillsboro, Oregon 97124-5961
SECRETARY: Matthew Flora (425) 869-2320, Fax: (425) 881-1008
mbflora@hyperlynx.com
Senior Engineer, HyperLynx, Inc.
17641 NE 67th Court
Redmond, WA 98052
LIBRARIAN: Jon Powell (805) 988-8250, Fax: (805) 988-8259
jonp@qdt.com
Senior Scientist, Viewlogic (formerly Quad Design)
1385 Del Norte Rd., Camarillo, CA 93010
This meeting was conducted in accordance with the EIA Legal Guides and EIA
Manual of Organization and Procedure.
The following e-mail addresses are used:
ibis-request@eda.org
To join, change, or drop from either the IBIS Open Forum Reflector
(ibis@eda.org), the IBIS Users' Group Reflector (ibis-users@eda.org)
or both. State your request.
ibis-info@eda.org
To obtain general information about IBIS, to ask specific questions
for individual response, and to inquire about joining the EIA-IBIS
Open Forum as a full Member.
ibis@eda.org
To send a message to the general IBIS Open Forum Reflector. This
is used mostly for IBIS Standardization business and future IBIS
technical enhancements. Job posting information is not permitted.
ibis-users@eda.org
To send a message to the IBIS Users' Group Reflector. This is
used mostly for IBIS clarification, current modeling issues, and
general user concerns. Job posting information is not permitted.
ibischk-bug@eda.org
To report ibischk2 parser bugs. The Bug Report Form Resides on
eda.org in /pub/ibis/bugs/ibischk/bugform.txt along with reported bugs.
To report s2ibis, s2ibis2 and s2iplt bugs, use the Bug Report Forms
which reside under eda.org in /pub/ibis/bugs/s2ibis/bugs2i.txt,
/pub/ibis/bugs/s2ibis2/bugs2i2.txt, & /pub/ibis/bugs/s2iplt/bugsplt.txt
respectively.
Information on IBIS technical contents, IBIS participants, and actual
IBIS models are available on the IBIS Home page found by selecting the
Electronic Information Group under:
Check the pub/ibis directory on eda.org for more information on previous
discussions and results. You can get on via FTP anonymous.
==============================================================================
Received on Thu Dec 10 13:02:31 1998
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