Subject: Quest for IBIS models

From: [email-masked] (Greg Edlund)
Date: Thu, 9 Feb 95 12:50:16 -0600

I took a peek into /pub/ibis/models the other day and found only
a small collection of models for Intel's CPUs and chip sets.
Am I correct in assuming that in order to procure IBIS models
for the parts on my board design, I will either have to

a. go to the mfgr's rep, or
b. buy a library from someone like Zeelan?

Have any of you found manufacturers yet who know what IBIS models
are?  I'm having a hard time trying to explain what SPICE models
are, much less get them in my greedy hands.  And SPICE has been
around a LONG time.  I'm just wondering how far we are along the
road toward creating an information exchange which is beneficial
to the engineer and does not give the manufacturer a migraine
and/or keep their lawyers up at night.

Thanks in advance.

--
Greg Edlund                +----+----+    "Years ago my mother would say to me,
Circuits and Modeling      |    |    |    'Elwood-' she always called me Elwood.
SuperComputers, Int'l.    <     |     )   'Elwood, in this world, you must be
1414 W. Hamilton Ave.      >  -----   )   oh-so-smart or oh-so-pleasant.'  Well,
Eau Claire, WI 54701      <   -----   )   for years I was smart.  I recommend 
(715) 833-7067 voice       >    |     )   pleasant.  You may quote me."
(715) 833-7096 FAX         |    |    |    Elwood P. Dowd 
[email-masked] email       +----+----+    (Jimmy Stewart in "Harvey")

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From: [email-masked] (Syed Huq)
Date: Thu, 9 Feb 95 12:51:53 PST

Hi Greg,

It's true that Intel is the only one who has released IBIS models but
within the next couple of months, you will see more and more models
being released from other semiconductor vendors.

National has just submitted a few models for release on vhdl.org and
more will follow soon.

I believe Xilinx is also releasing models sometime in March.

Stay tuned.
Syed.
National Semiconductor.

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From: Arpad Muranyi <[email-masked]>
Date: Thu, 9 Feb 95 13:14:03 PST

Text item: 

Greg,

Most vendors are reluctant to give out SPICE models even if they have it (and 
regardless that SPICE has been around for about 20 years), becuase those kind of
models give away all their secrets.  You should have better luck in pursuading 
them to make IBIS models, because those are accurate, but still safe regarding 
propriatary material.

Even though there are not many models on vhdl.org, we are hoping to get more and
more companies to start making models.  In order to achieve this goal, we need 
people like you (who need models) to contact IC manufacturers and express your 
needs.  It is a painful process, but demand drives market.

Arpad Muranyi
Intel Corporation

Thanks in advance.

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From: Mark=Leonard%CAE%PCPD=[email-masked]
Date: Thu, 9 Feb 95 15:58:31 CST

Greg,

My experience in getting Spice and/or IBIS models has varied dramatically from 
vendor to vendor.  As this might also be of some interest to the various tool 
vendors, here's my feedback...

My starting point is usually the vendor's rep.  Inevitably the rep has no clue 
what we're requesting, though they do come up to speed fairly quickly.  Within 
a day or so I get feedback as to what's available.  An increasing number of 
companies have Spice information readily available, and a small number have 
v1.1 IBIS stuff available.  I've yet to see a v2.1 model (though Intel has 
provided equivalent Quad and HSpice models for buffers that couldn't be 
accurately modeled in the earlier format).  Interestingly enough, many of the 
companies I've encountered that have IBIS models also are willing to provide 
the original Spice info.

I make a point to try to get my hands on Spice models for several reasons 
(even though I won't be using Spice to run the sims).  First off, we've had 
some success in getting vendors to "guarantee" their Spice models.  I rarely 
get guaranteed IBIS models (it's happened once, and wasn't a memorable 
experience).  Secondly, I can gain some insight into the model accuracy by 
looking through the netlist and device models.  Though this can be misleading 
it can also be quite beneficial.  I have a big issue with non-guaranteed 
models, but that's another subject.  Finally, with most Spice models you're 
free to set the operating conditions (process point, voltage, and temperature) 
according to the each system's specifications.  IBIS min/max conditions are 
often predefined and accordingly are too conservative for some applications.

When Spice models aren't available or can't be obtained in an acceptable time 
period (the lawyers got involved), I take one of two different approaches 
depending on my needs.  Sometimes I'll ask for IBIS models, while other times 
I'll ask the vendor to perform a series of buffer characterization sims and 
simply send me the raw results.  The second approach has worked well when the 
vendor doesn't have IBIS models, doesn't know what IBIS models are, has v1.1 
models that aren't accurate enough, or has the wrong operating conditions in 
their standard models.  These two approaches have worked well at times, while 
other times the whole experience is a big pain in the [insert favorite 
anatomical reference here].

As to Zeelan models, they could come in handy at times.  I've yet to purchase 
a copy of their library for two reasons:  it doesn't contain min/max models 
and doesn't contain all the parts I think it should (DRAMs, cache RAMs, etc.). 
 There have been times, however, when it would've been beneficial to have 
their library available.

As to industry trends, I've seen a positive shift over the last 6 months or 
so.  In general most of the companies have a long way to go, but I get the 
impression that more and more of 'em are heading the right way.  I know I've 
been going to a lot of trouble to educate a number of 'em...

Mark Leonard
Lead Engineer, Signal Integrity Group
Compaq Computer Corporation

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From: Fred Vance <[email-masked]>
Date: Thu, 9 Feb 95 17:02:23 -0800

Jon,

I stand corrected. I hold too limited a view of a model. Information for the behavioral  
specification of IC I/O analog characteristics is indeed a model.

I tend to think of a model as something that I can use directly to analyze and/or simulate  
circuitry, like an XTK model or a SPICE model.

Thanks for the tip on IBIS2XTK. I've had XNS ver. 5.3 installed for a month now and didn't  
realize it was there. I notice that it was available in ver. 5.2, but for some reason, I missed  
that version. I'll give IBIS2XTK a try on some of my IBIS data.

For all my SPICE models, do you recommend using S2IBIS and IBIS2XTK or just SPI2MOD?

I'm working on getting an updated version of HSPICE, maybe they will have a converter as you  
say and life will be much easier. I sincerely look forward to the day when everyone provides  
IBIS information... I mean models.

Regards,
Fred
FirePower Systems, Inc.

Begin forwarded message:

Date: Thu, 9 Feb 95 14:31:03 PST
From: [email-masked] (Jon Powell)
To: [email-masked]
Cc: [email-masked],
        [email-masked]
In-Reply-To: Fred Vance's message of Thu, 9 Feb 95 13:26:02 -0800  
<[email-masked]>
Subject: Quest for IBIS models

Greg,

I must heartily DISAGREE with Fred from FirePower.

IBIS is a behavioral model standard.

IBIS models, though quite usable as SPICE behavoiral models, are also equally usable
by the various non-spice offerings of Quad, Hyperlynx, Cadence, Quantic, Interconnectix etc. 

(sorry who-ever I left out). These non-spice companies have been IBIS compatible since the
creation of IBIS (some even before) and have been some of the stronger driving forces
in the establishment of the IBIS standard (partially because they pioneered the behavioral
model representation). All of the IBIS associated companies have IBIS converters or can 

read IBIS directly, all have different strengths etc.

regards,

jon powell
Transmission Line Products Manager, Quad Design.