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Re: gEDA-user: gEDA flow for chip design?


an excerpt from above section:
"Convergence and noise modeling were key issues. At each change, I had
to learn about the new tool and adapt the models and circuit files to
the new simulator. As you can imagine, all that cost a huge amount of
time, though I learned a lot. Different simulators have different
MOSFET models and adapting parameters from one to another can be difficult.
HSpice is the "big bucks" professional tool that the foundry's model
parameters often target. Fortunately, I was able to get temporary
access to it to complete the design."

He takes a pragmatic view, aiming for results where he could not afford to fail
by aiming at "an easy commercial design", avoiding letting the scope enlarge
during his project, and choosing the mainstream proprietary tool based
on old open source Berkeley SPICE.  It's tempting to fall into that
thinking and abandon open tools, but John Doty has a work flow figured out
with NG-SPICE and no proprietary tools except maybe layout.

Another way you might get around
the convergence problems and get even better performance than
Doty is to use gnucap.  Al says he's done tests
on large circuits to make it perform well and converge better than
many versions of SPICE.  Not yet tested by me though.

There are some hurdles to using gnucap -- I had a hard time
getting a wave viewer installed on my debian linux computer -- neither
gtkwave nor gwave are easy except on Red Hat due to some good packaging
effort by Chitlesh et al:

debian has a new version of gtkwave since I last used it, so
I'm installing and...  there aren't any examples for gnucap
I can find.

Would gnuplot work OK for gnucap?  I've used it since forever and
it might even be fast now...

Here's a recipe I found searching for a gtkwave gnucap example
that suggests scripting gnuplot is less hassle than getting gwave to build...
So it could be used for gnucap as well as gwave or gtkwave, right?

John Griessen
no longer a chip designer, but thinking of down-to-the-material circuit design
for printable organic semiconductors soon.  That will reset circuit density to 1978 levels,
but be throw away cheeeep to print.

A much simpler and more convenient way is using gnuplot, mimicking
gwaveâs behaviour for gspiceui.
Put the following into the file â/usr/bin/gwaveâ:


HEAD=`head -n 1 â$FILEâ | tr -s â â`
COLS=`echo $HEAD | wc -w`

echo plot â\â
for x in `seq 2 $COLS`
echo -n â â \â$FILE\â using 1:$x with lines ti \â`echo $HEAD | cut -d â â -f $x`\â
if [ ! $x -eq $COLS ]
echo -n â,\â
} | gnuplot -persist

That way you simply can click the âplotâ button. gnuplotâs window will pop up and show the plot automagically.

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