RE: [SI-LIST] : ibis or spice?

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From: Todd Westerhoff (twester@hhnetwk.com)
Date: Thu May 03 2001 - 07:42:16 PDT


The answer to your question is: it depends.

IBIS is actually a language for characterizing I/O behavior that has a
defined structure and syntax. That's the long way of saying it models a
defined subset of all possible I/O behavior. SPICE, on the other hand, can
model anything. Want to model viscous fluid flow through a pipe? Sure -
come up with the correct electrical equivalent model, and SPICE can handle
it for you.

So, "it depends", means that you have to understand the interconnect and I/O
you want to analyze, and whether or not behavioral analog simulation will
model enough of the effects properly to give you a reasonable answer. If
IBIS provides an adequate answer, then by all means, use it. And, if IBIS
won't give you the detailed answer you want, you still may be better off
running IBIS up-front to get you in the ballpark, before you run a SPICE
analysis. This is especially true if you're running pre-route analysis and
looking at a number of different scenarios. We regularly analyze hundreds
and thousands of "variations" at a time using IBIS models, receiving answers
within minutes. You can imagine what the turnaround time would be if we
were doing things differently.

But for I/O structures that IBIS cannot address, SPICE may be your only
choice. And for critical applications, it's almost always worth the effort
to look at structures with both forms of simulation, to make sure the
answers correlate.

I view simulators as tools. They help you get a job done, but you have to
understand what their limitations are, how to use them, and to which
problems they are best applied. Please don't expect a simulator or SI tool
to give you an answer - because it won't. Its purpose is to give you data -
on which you can base design decisions.

Todd.

-----Original Message-----
From: owner-si-list@silab.eng.sun.com
[mailto:owner-si-list@silab.eng.sun.com]On Behalf Of John Zhang
Sent: Wednesday, May 02, 2001 8:04 PM
To: si-list@silab.eng.sun.com
Subject: [SI-LIST] : ibis or spice?

Question for model users:

What is the preferred model and why? IBIS or Spice?

I know people who hate IBIS and people who like IBIS.
So far, I've yet to meet someone that hates Spice.

Any comments as to which models you would prefer?

Thanks.

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