Re: [SI-LIST] : IBIS models

Laurence Michaels (
Mon, 30 Aug 1999 14:51:27 -0400

Roy Leventhal wrote:
> Abe,
> Not always so simple and convienient as you indicate. I agree with you for a
> device witha few tens of pins. But, for example, for a programmable device with
> several hundred pins it's a lot of tedious extra work for every user of the
> device. A lack of a proper pin list is just a lazy supplier's way of avoiding
> the same distasteful, resource consuming task their customers would find more
> cost effective if it were just figured into the price of the part.
> IBIS itself offers no real sanctions for non-compliance with any of its
> provisions. When the JEDEC committee tried laying down the law to suppliers they
> were quickly rendered irrelevant with the use of "supplier controlled,
> non-registered data sheets." Talk about a license to do anything at any time to
> your product with warning or data.
> I still haven't figured out what the disclaimer "Data is for modeling purposes
> only - - - use at own risk - - - not guaranteed," etc. Just what do suppiers
> think I should do to proceed with my design, improve its insensitivity to normal
> process variation, not overstress it, etc.?
> I don't get it. I thought that IBIS was an agreement between semiconductor
> supplier and software suppliers to provide an improved means for exchanging data
> with their customers so that they could all suceed together. How do half-assed
> pin list help that objective?
> Best Regards,
> Roy
[snip log of previous messages]

"Data is for modeling purposes, etc." language is usually just copied
from the IBIS standard document. As for what it means, well, welcome to
the litigious society. Apparently vendors are scared we might use this
(fairly specific) data to design something, and then sue them when it
doesn't work the way the IBIS file says it does.

Hmm... There's an idea ;-)

IBIS seems to be an agreement between Some semiconductor suppliers, and
Some software suppliers. Nowhere near all, and I keep finding IC
suppliers that have less than 1 clue about IBIS. Many of them haven't
integrated IBIS modelling into their design process, so IBIS models are
not done unless some customer asks for them. In which case, "Please
wait six weeks while we figure out what you're talking about" seems to
be a common refrain. Some of the time, there's only one person at the
company who does IBIS, and he's also a VP of something, so you know how
much free time he probably has (NONE).

And I hate getting the "We don't usually do this, but as a courtesy,
we'll do it this time." line.

I suspect generating IBIS models would be much simpler if it was done as
part of the IC vendors design process, and not tacked on as an
afterthought. Wishful thinking?


Laurence Michaels
Simulation Support Engineer - General Datacomm, Inc.
The light at the end of the tunnel is the muzzle flash.

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