( SNUG 99 Item 28 ) ----------------------------------------------- [3/31/99]
Robert Wiegand of Ensoniq Corporation presented a unique MIN/MAX method
to stop the ping pong effect which is common when using the characterize
command to optimize the timing of a design. (The ping pong effect is
where the synthesize/characterize iterations cause worst case delays to
alternate, or hop, between two modules that contain the path.) Robert's
technique requires three synthesis/compile passes. The first pass
compiles the RTL with default constraints, the second pass compiles with
the constraints derived from the characterize, and the third pass does an
incremental compile with the constraints derived from the characterize.
The key difference from the "normal" methodology is the incremental
compile, which is supposed to put a stop to the ping pong effect.
"Cooley, Golson, and Baty were really going at it in the bar over
that MIN/MAX compile technique. Golson and Baty hated it because
it created designs with overly conservative wireloading. Cooley
loved it because it completed designs quickly. Those three
squabbled for a good half hour. Brainy little kids, actually."
- Anon
"Weigand's MIN/MAX paper was well researched, well written, and well
presented. Even the slides were well done. It was perfect in every
way. I would have given it a 5.0 rating [the highest] in the user
survey. I just completely disagreed with what it was saying."
- consultant Kurt Baty
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