what buttons do you push, i.e. what rules did you find significant playing
around with? Just being curious ...


Gisbert Auge
N.A.T. GmbH

                    "Bagotronix Tech                                                   
                    Support"                  An:     "Protel EDA Forum" 
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                    <techsupport@bagot        Kopie:                                   
                    ronix.com>                Thema:  Re: [PEDA] Autorouter            
                    16.11.2001 16:06                                                   
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                    "Protel EDA Forum"                                                 

How large is large for you?  I use the 99SE autorouter for my "large"
designs, but not for small designs.  It takes a lot of practice and
trial/error to figure out how to set up the autorouting rules for each
board.  And each board may take different rules.  You just have to have
patience.  Typically I will spend a half day tweaking rules and testing
with trial routing runs.  After you get an acceptable run, you will need to
do some manual cleanup.  Yes, it doesn't seem very productive.  But it is
still faster than routing the whole thing manually.

When I say "large", perhaps a better metric is "difficult".  Our DOS Stamp
is a 6-layer PCB with only 10 ICs on it, but it is very small (2.6 x 2 in.)
and has SMT parts on both sides.  Not a large design, but quite difficult
given the small area and parts on both sides.  The router does a good job
this board with the right rules.

Another board I did recently was a PC/104 form factor 486-class custom SBC.
8 layers (2 power, 1 ground, 5 signal), 2 large PQFP208 devices and 12
ICs.  The router did a good job on it.  An afternoon to tweak the rules,
30 minutes to clean up afterwards.

If you have lots of replicated circuitry with parallel, ordered busses, you
can probably do better with manual routing.  But if the circuitry lays out
"randomly", as most of mine do, autorouting is a more productive choice.
The pinouts of most of the chips and the placement of I/O connectors are
constraints you cannot do anything about.  If you have PLD/FPGAs, you can
control the pinout of these devices somewhat.  I tend to let the PLD/FPGA
fitter do pin assigment, because I want the best utilization of chip
resources.  But the more large chips you have in your design, and the more
vendors of chips, the more random your layout will be.

Work with the router for a while.  Everything in autorouter lore says it
should be a "pushbutton" process.  They don't say how many buttons you have
to push to get good results!  Also, keep in mind that an autorouter will
never be as smart as you, only faster than you.

Best regards,
Ivan Baggett
Bagotronix Inc.
website:  www.bagotronix.com

----- Original Message -----
From: "Tim Fifield" <[EMAIL PROTECTED]>
To: "Protel EDA Form" <[EMAIL PROTECTED]>
Sent: Friday, November 16, 2001 9:07 AM
Subject: [PEDA] Autorouter

> Just curious... Does anybody use the 99SE autorouter for large PCB
> Do the majority of board designers do everything manually? I don't even
> bother with the autorouter anymore, it's to messy. Perhaps I'm not
> it up properly. What do you people do?
> Tim Fifield

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