( ESNUG 274 Item 8 ) --------------------------------------------- [12/10/97]
From: erez@taux01.nsc.com (Erez Naory)
Subject: What's Better? "Rich" Or "Sparce" Synopsys Libraries?
Hi, John.
I have been involved in an effort of generating Synopsys libraries.
The target is to be able to compile a design to the fastest speed. One of
the questions that arises is how "rich" the library should be? Some
libraries out there have over 1000 cells, but, on the other hand, some have
much fewer cell selection (~300). I know, theoretically, more is better,
but I have seen cases where it does not apply. For example, we had a
complex gate that had (by mistake) only one size. Removing the cell made
the design synthesize to a faster speed. It seems like Design Compiler
picked up this cell, assuming it could bump up the size, but then when it
found out it cannot do that, it could not recover.
Does any one has any experiece with this? Is there a DC runtime penalty
for using the rich libraries vs sparce libraries?
- Erez Naory
National Semiconductor Hertzlia, Israel
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