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

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From: Fred Balistreri (fred@apsimtech.com)
Date: Tue Nov 16 1999 - 13:03:14 PST


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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