( ESNUG 420 Item 10 ) ------------------------------------------- [10/22/03]
From: Tobias Thiel <r44235=user domain=motorola spot calm>
Subject: Is Anyone Really Using SPDM/SPPM Libs? What Tools Use Them Now?
Hi John,
For features like Dynamic Voltage Scaling or timing analysis that takes
into account IR drop we are thinking about replacing our current Look Up
Table libraries with equation based libraries.
While Synopsys is constantly asking us when we would switch to Scalable
Polynomial Delay Models (SPDM) in our libraries, our libraries group has
been looking into this for quite some time and found that these libraries
are not ready for production use yet. The main obstacles are the accuracy
of SPDM and SPPM, the high characterization runtime, and the lack of support
for these libraries by tools other than those from Synopsys.
I would like to ask the Synopsys users about their experiences with SPDM.
- Is anyone really using SPDM/SPPMs?
- How much overhead do you see in generating the libraries?
- Which tools can read SPDM/SPPMs (Synopsys and non-Synopsys)?
- Is there a performance impact when using SPDMs?
- How good is the accuracy compared to traditional Look Up Tables?
I had a short chat with two engineers from the library group of another
company. They told me that they also looked into SPDM and were not at all
satisfied with this modeling approach for basically the same reasons.
Especially the curve fitting when using higher order polynoms they said
would potentially result in bad accuracy. Is their story unique?
- Tobias Thiel
Motorola GmbH Munich, Germany
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