( ESNUG 406 Item 11 ) ------------------------------------------- [02/12/03]
Subject: ( ESNUG 405 #2 ) Odd Blocks From Floorplan Compiler Choke PhysOpt
> We taped out a design last April using Jupiter/Physopt/Apollo and one "U"
> shaped rectilinear block. The block had pins on 6 of the 8 sides. ...
> Surprisingly we found only one problem with the entire rectilinear flow.
> At the time, the Jupiter function to align the pins of adjacent blocks
> didn't work on our "U" block. I don't know if this has been fixed or not
> in later rev.'s.
>
> - Jon Stahl
> Avici
From: Russ Petersen <penguin=russp iceberg=subasic.sciatl shot balm>
Hi, John.
OK, I have to resond to this as we've had some trouble here. We have been
successful using Floorplan Compiler to create rectilinear blocks and then
passing them off to Physical Compiler, although some significant problems
with PDEF kept coming up again, and again, and again, and again. Does it
sound like I'm tired of the PDEF problems? Hey, and its even Synopsys who
came up with PDEF in the first place, right? Enough with the PDEF problems.
:-)
One thing we did learn was this: Don't ever put a notch in the bottom left
corner of your block (ie: don't make a rectilinear block that would notch
out the traditional origin) if you are going to be using Physopt. Ex:
************************
* *
***** *
* *
0,0 ********************
We had a block that looked like this and PhysOpt (no matter what version)
completely fell apart on it. We eventually got it to work with some
creative workarounds but it was painfull and slowed us down. Hopefully this
will get fixed with an upcoming version as Synopys has been made very well
aware of this problem and the pain it caused us. Since I didn't work with
the block directly I can't remember the final fix or all the issues but it
was doing things like shifting all cell up and to the right, messing up the
pins, etc... In short, it was making a mess of things.
Finally, FPC has a current weakness in that while you can create rectilinear
blocks OK from the start, but you can't easily modify them with the GUI.
That is, if you try to stretch a side it just reverts back to a plain
rectangle. Hence, any adjustments have to made from the command line using
actual coordinates for the corners. Synopsys has been made aware of this
however so it should hopefully be fixed soon.
- Russell Petersen
Scientific Atlanta Lawrenceville, GA
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