[ibis-macro] Re: [ibis-interconn] Re: We need to define terms System, Component, Connected, Connection, Module, .ibs Package and Die, .ibs Bare Die

  • From: "Walter Katz" <wkatz@xxxxxxxxxx>
  • To: "'Lynne C. Green'" <lgreen22@xxxxxxxxxxxxxx>
  • Date: Fri, 8 Feb 2013 18:34:56 -0500 (EST)



I define a package as containing one die, and therefor can be described in
a .ibs file. A Multi-Chip Module contains two or more die (multi means
more than one!), although I think it would be perfectly OK for a EMD
containing a single die. This is a semantically difference, but also has
practical usage. EMD are truly post layout, while .ibs files are often
used to describe pre-layout. .ibs files are often delivered by IP vendors
or ASIC vendors to describe the simulation properties of a buffer or a
Tx/Rx buffer pair. It is also common in a package for the IC Vendor to
describe a Typ/Min/Max package interconnect subckt for all of the Models
in a bus, so the difference in interconnect models for an EMD that
represents a package and single die and a .ibs file is that the EMD is
strictly post layout, while the .ibs file can be either post layout
(subckts between the pins and die pads) or pre-layout where the subckt is
defined between the pins and die pads of all the connections to a [Model].
Crosstalk in an EMD is between actual connections.   Crosstalk in a .ibs
model is between actual connections or between and connection and other
connects in the bus, but not necessarily to specific connections.   This
reflects the various ways that IC Vendors are currently delivering package
interconnect models.




From: Lynne C. Green [mailto:lgreen22@xxxxxxxxxxxxxx] 
Sent: Friday, February 08, 2013 5:28 PM
To: Walter Katz
Cc: 'IBIS-Interconnect'; 'IBIS-ATM'
Subject: Re: [ibis-interconn] Re: We need to define terms System,
Component, Connected, Connection, Module, .ibs Package and Die, .ibs Bare


Thanks, Walter,

Interesting.  Of course, answers always create new questions...

New nits:
- I love Walter's statement that "connection" could include a DC blocking
cap.  Since that is highly clarifying, perhaps it could be added to the
definition, to emphasize impedance is checked at Nyquist freq? (might need
to spell out Nyquist for the newbie, but that is a different can of worms)
- On second definition of "Connection", plural?
- Newbie question: How is "package" different from "module".   i.e. could
a newbie confuse the two, or perhaps take advantage of features of one
that are not in the other? (not that any IBIS model maker has ever done
that before ;-)
- If there is a difference, is there any "easy" way to make module and
package work the same way (one vs multiple chips, multiple chips in
packages, so they start looking more alike over time).  Am I seeing a
difference of naming, or concept, or syntax, or a real physical


On 2/8/2013 12:43 PM, Walter Katz wrote:



First definition is for "Connected" fixed below. A connection may have a
blocking cap. At DC it is high impedance, but will be low Impedance at
Nyquist. Of course "Low" or "Small" impedance is not very precise. A long
connect with a blocking cap could have in insertion loss of ~30dB at


A bare die is mounted in a Module. The wire bond is in the Module
interconnect and is accounted for in the Module interconnect module,
similar for flip mounted.




From: ibis-interconn-bounce@xxxxxxxxxxxxx
[mailto:ibis-interconn-bounce@xxxxxxxxxxxxx] On Behalf Of Lynne C. Green
Sent: Friday, February 08, 2013 3:21 PM
To: IBIS-Interconnect
Subject: [ibis-interconn] Re: We need to define terms System, Component,
Connected, Connection, Module, .ibs Package and Die, .ibs Bare Die



My usual nits, from a "newbie" viewpoint.

Where will the interconnect between bare die and package be accounted for?
It is not in the IBIS [Model] or the Component [Pin] list.  And apparently
not in "Interconnect Subckt".  Presently accounted for in [Package Model].

Quibbles on zero ohm impedance. 
a) bare die, where wire bond is the package.  Package impedance
approximately 1nH, varies with wire bond length. 
b) bare die, flip mounted (on module or another die).  Package impedance
approximately 0.1nH. 
Neither case is negligible at 100Gb/sec (alpha prototyping now). 

Having two definitions of "Connection" is confusing me.  In simulation, a
"node" means a dead short - one node number, negligible impedance, etc.
While I can see the first definition, the second one is confusing me.

Other than those nits, this is definitely clarifying things for me.


On 2/8/2013 8:00 AM, Walter Katz wrote:



There has been two much confusion on what EMD is and a comprehensive .ibs
package and on-die interconnect solutions, so I propose the following
definitions to clarify future discussions.



A system consists of multiple components that have electrical connections
between them.


A basic building block of a System. A component can be a backplane, PCB,
Connector, Cable, DIMM component, Multi Chip Module, Interposer, package,
a packaged die, a bare die, and other things that have not been invented


Two electrical nodes in a system are connected if the Insertion Loss
between the two points at Nyquist is "Small". 


A connections consists of a list of electrical nodes that are all
connected to each other.


A Module is a Component that has Pins that connect to other system
components, and contains Components and Connections between these
Components, and between these Components and the Module's Pins.


One proposed solution that describes Interconnect Subckts between the
Module Pins and/or Module Components Pins

IBIS Component

Represented by a .ibs file, contains one, and only one die, [Models],
package interconnect between the [Component] [Pins] and Die Pads, on-die
interconnect between the die pads and the [Model].

Bare Die IBIS Component

A special case IBIS Component that represents a physical Die that is
mounted directly in a Module. An example of this is a multi-chip module
(MCM) that contains two are more die that are mounted and wire bonded
directly on the MCM surface. The [Pin] and on-die pad are at the same
location, and the Package model should be treated as a zero ohm resistor.

Interconnect Subckt

An IBIS-ISS subckt or a Touchstone File that has ports that as described
below. The ports may or may not be connected to all of the other ports.



Component Pins

IBIS Package


Die Pads

On-Die Interconnect

Die Pads

[Model] ports


Note that a Module (and therefore EMD) never has connections to [Model]!!!







Walter Katz


Phone 303.449-2308

Mobile 303.335-6156




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