Subject: Re[2]: BIRD 6.1

From: Will Hobbs <[email-masked]>
Date: Mon, 31 Jan 94 15:17:48 PST

Bob, et al,

Just to reassure you, the main reason IC vendors' participation is so crucial to
IBIS is that they have the proper equipment and design and technology databases 
needed to create the IBIS models.  Some companies also can generate them from 
characterizing ICs.  To date, I am unaware of anyone creating an IBIS model from
published data book data, except when the data was already in IBIS format, such 
as the 82430 PCIset from Intel.  Regarding where to get tskew information, 
again, I don't feel the data books are the right place to go, either.

Regards,

Will Hobbs
Intel Corp.
>
> Hello IBIS members:
>
> Here is an updated BIRD6.1 to reflect the discussed and emailed changes.
> I would appreciate any comments or corrections from Kellee, Syed, Bob Ward, 
> Jon, and anyone else as to whether this version meets the simulator needs
> and also contains information that is easily available from data sheets and 
> from vendors.  I am particularly concerned that "tskew_min" is meaningful. 
> I am also concerned whether the normal test setup for tskew in data books
> which include 50pF/100pF loads gives overly pessimistic values.  If 
-you wish,
> you can reach me at (503) 684-6641, fax (503) 639-3469 or send email.

Regarding your statement:
"I am also concerned whether the normal test setup for tskew in data books
 which include 50pF/100pF loads gives overly pessimistic values."

If data book numbers are copied into IBIS models without verifying 
simulation vs. time-domain measurements, then the data book capacitance 
numbers could lead to faulty simulations.  Faulty simulations, even if they 
do provide conservative results, are a nuisance.  We don't like finding out 
that we have spent labor fixing problems that didn't really exist.

We rank models based on our confidence in them & models created from data 
book info have the lowest ranking.  The same driver with 2 different 
package models can have very different waveforms.  If an IBIS model uses 
data book info, the model should have a disclaimer to say so.

--
Bob Canright		Convex Computer Corp.	Richardson, Texas 
214-497-4474 (desk)	[email-masked]	214-497-4500 (FAX) 
disclaimer:
It's not my typing, the Sun keyboard repeeeatsss.