Re: IBIS Subcommittee Formed to Review Spice to IBIS

From: D. C. Sessions <dc.sessions@vlsi.com>
Date: Thu Jun 10 1999 - 16:31:55 PDT

Aside: maybe we should take the [SI-LIST] out of the Subject?

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.

I'm having a problem with this, Jon. With inflection points chosen using
the usual spline algorithms, 100 points should be enough for almost ANY
monotonic transition. Oddly enough, I don't disagree with increasing
the point count, but "you can't model it accurately otherwise" just isn't
obvious to me.

Could you give us an example?

> 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

-- 
D. C. Sessions
dc.sessions@vlsi.com
Received on Thu Jun 10 16:38:47 1999

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