Re: [SI-LIST] : IBIS datasheets for PCI and DDR

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From: Rachild Chen (rachel.chen@huawei.com.cn)
Date: Tue Nov 16 1999 - 17:57:05 PST


Ha..Ha,Amen!

There is so many people caring about the modles like me.I have a big trouble in models.I ever asked IC vendors for the spice models by NDA.But they gave me the macro spice models and have many mistakes.It need many times feedbacks
when I get the right spice models.It is too troubling.

In the same times,I get many IBIS models from IC vendors.So many errors in these models .I think they are trash and give us too much error informations.So I want to know how you treat models.

I think the IBIS needs improvement and considering more parameters to meet high speed analyse.

Regards,

Rachild

Fred Balistreri wrote:

> Scott McMorrow wrote:
> >
> > Chris Cheng wrote:
> >
> >
> > spice only for DDR i/o but then again, why do
> > u need ibis if u have the full spice......
> >
> > Lets see ...
> > Faster performance in simulation by 10-100X ...
> > Encapsulation of standard measurement points ...
> > Encapsulation of package parameters ...
> > Equivalent or better accuracy depending on method of
> > creating and characterizing the model ...
> > More widespread simulator support.
> >
> > Hmmm ... I can't imagine what the need or desire for
> > IBIS models would be.
> >
> > regards,
> >
> > scott
> >
> >
> > --
> > Scott McMorrow
> > Principal Engineer
> > SiQual, Signal Quality Engineering
> > 18735 SW Boones Ferry Road
> > Tualatin, OR 97062-3090
> > (503) 885-1231
> > http://www.siqual.com
> >
> >
> > Name: scott.vcf
> > Part 1.2 Type: text/x-vcard
> > Encoding: 7bit
> > Description: Card for Scott McMorrow
> I agree strongly with most of the statements but disagree with the
> accuracy issue. Assuming that the SPICE model is correct and the IBIS
> model is correct, there is no way that an IBIS model can be more
> accurate than a SPICE model. This is regardless of where the IBIS
> model came from. Keep in mind that MOST IBIS models are produced from
> the SPICE model using s2ibis. That means by default MOST IBIS models
> cannot be more accurate than the source. For one thing SPICE is a
> different animal and contains much more information regarding both the
> topology and process of the design. Secondly there have been and
> continue to be accuracy as well as other issues with IBIS. If this were
> not the case there would not be 64 birds to date and counting.
>
> Both the IBIS and SPICE model are prone to incorrect data. Being not
> correct is NOT the same as model accuracy. In my view both SPICE and
> IBIS models have their application. There is some overlap in the SI
> community. You probably should not use SPICE models to simulate a
> whole board. But accuracy is a different issue. For most SI applications
> IBIS will do. But there are cases where one may need the SPICE model.
>
> Best Regards,
> --
> Fred Balistreri
> fred@apsimtech.com
>
> http://www.apsimtech.com
>
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