( ESNUG 331 Item 8 ) --------------------------------------------- [10/7/99]
From: [ Kenny from South Park ]
Subject: Help! I'm Being Sucked Into The DC Billion Switches Black Hole!
Dear John,
Recently, I've been having fun with Synopsys switches. Somewhere between
the "compile_new_boolean_structure", and "hdl_use_cin" I've come up with at
least 14 known switches that modify the synthesis of your design in a major
way. That means that there are at least 2**14 possible combinations of
those switches, plus the ones I haven't encountered yet, plus the ones they
don't tell you about. From the synthesis errors I've been getting lately,
I wonder how many of these combinations have actually been tested Synopsys.
My guess would be not many.
After fiddling about with the problem for awhile, I've decided that the
only way to deal with this situation is to limit the number of "non-default"
switches a user can set to 1, or 2 at most. Some switches, while they
worked together just fine in the 97.08 version, no longer "play well
together" in the 99.05 versions. Alot of this may have to do with patches.
After 3 patches to 98.08 and two so far to 99.05, I'm having difficulty
keeping up! This limits the designer greatly, but without formal
verification what else can you do? It seems that you can't trust Synopsys
synthesis any more.
- [ Kenny from South Park ]
|
|
