Re: [SI-LIST] : IBIS Subcommittee Formed to Review Spice to IBIS

Scott McMorrow (scott@vasthorizons.com)
Tue, 08 Jun 1999 17:00:31 -0700

I second Jon's opinon.

There is no real reason to limit the number of points in
IV or VT tables. I have often used a simulator which allows
an arbitrary number of points over 100 to create high
resolution simulations. 256 to 512 is often useful to
capture rising edge timing information accurate to 1ps, along
with driver overshoot behavior to within 1 mv of HSpice
simulations.

Model size makes no difference to me. It is the result that
matters.

Scott McMorrow
SiQual

jonp@pacbell.net wrote:

> I agree with Weston.
>
> Either that or remove the quite artificial limit of number of points in an IBIS
> file.
> I have actually been faced with the problem that even with software to remove
> extra points I cannot
> create IBIS models to the accuracy that I desire with the 100 point limitation.
>
> jon powell
> Viewlogic Consulting Services
>
> Beal, Weston wrote:
>
> > Kellee,
> >
> > You're disagreeing a mute point. Your point was the same point I was trying
> > to state by saying, "the IBIS creator tool should have an algorithm to
> > remove points in linear regions." We should delete all these extra data
> > points. The problem that s2ibis has now is that all points are equal
> > difference. They should be closer in knee points and very sparse is linear
> > regions. The IBIS creator tool should have an algorithm to clean out extra
> > data.
> >
> > So, I agree with you and now you can agree with me.
> >
> > Later,
> > Weston Beal
> > Signal Integrity Engineer
> > Compaq Computer Corp.
> >
> > -----Original Message-----
> > From: Kellee Crisafulli [mailto:kellee@hyperlynx.com]
> > Sent: Monday, 07 June, 1999 2:19 PM
> > To: Beal, Weston; ibis@eda.org
> > Subject: RE: [SI-LIST] : IBIS Subcommittee Formed to
> > Review Spice to IBIS
> >
> > Hi
> >
> > I have a comment on Weston's comment on the number of data
> > points.
> > I disagree on one point. Instead of increasing the number
> > of points generated
> > in the IBIS file the spice to IBIS tool should improve the
> > quality of the
> > points
> > choosen.
> >
> > I can hand build files with 50 points that out perform files
> > with 400 points.
> > The big gain is that the FILE SIZE is reduced with higher
> > accuracy.
> > Large IBIS files will take up many megabytes on 1000's of
> > hard drives.
> > The V/I and V/T tables are the largest part of IBIS files.
> > Increasing them 4 x will generally increase the file size 3
> > x or more.
> >
> > >The third thing that I changed was the number of points in
> > the time
> > >waveforms from 50 to 101. I have to remove one point to
> > comply with the
> > >golden parser, but I get better detail. On the issue of
> > number of points in
> > >a curve or waveform, I think the user should be able to
> > define any degree of
> > >granularity and the IBIS creator tool should have an
> > algorithm to remove
> > >points in linear regions. If the resulting curve still has
> > too many points,
> > >then increase the linearity tolerance and try it again.
> >
> > Best wishes...
> > Kellee