I'm not at my Protel workstation today, so this is from memory...

I find that your choice of direction bias on the routing layers can make a
big difference.  I will try several trial runs with different choices to see
which one has the best results.  You should make use of the 45 up, 45 down,
fanout (on top layer, and bottom layer if parts on both sides).  The manual
says to always use pattern and memory algorithms - I say try it with and
without.  Sometimes you will get better results on "random" nets if you
don't use either or both of these algorithms.  Be sure to set high
priorities for high-speed nets (clock lines, strobes, etc.) so they get
routed first and most direct.  Also, choosing the type of net routing (daisy
chain, star, load terminated, etc.) can be important.  The from-to list will
have to be edited to get the desired routing on some nets.  This is easy,
but takes some getting used to.

The router will do funny stuff with power and ground plane via connects.
You will have to cleanup these connects manually after autorouting.  The
funny behavior you will see is multiple connections to a plane and strange
stubs.  Protel needs to improve this aspect of the router.  Another thing I
have seen happen is when using split planes, a via connection to the plane
may be made outside the boundary of the plane.  This gets flagged as a DRC
error (thankfully!), but is a problem with the router.  So, don't use split
planes if you use the router.  Protel needs to fix this too.

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

----- Original Message -----
To: Protel EDA Forum <[EMAIL PROTECTED]>
Sent: Friday, November 16, 2001 10:29 AM
Subject: Re: [PEDA] Antwort: Autorouter

> Ivan,
> what buttons do you push, i.e. what rules did you find significant playing
> around with? Just being curious ...
> Regards,
> Gisbert Auge
> N.A.T. GmbH
>                     "Bagotronix Tech
>                     Support"                  An:     "Protel EDA Forum"
>                     <techsupport@bagot        Kopie:
>                     ronix.com>                Thema:  Re: [PEDA]
>                     16.11.2001 16:06
>                     Bitte antworten an
>                     "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
> them
> with trial routing runs.  After you get an acceptable run, you will need
> 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
> 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
> on
> this board with the right rules.
> Another board I did recently was a PC/104 form factor 486-class custom
> 8 layers (2 power, 1 ground, 5 signal), 2 large PQFP208 devices and 12
> other
> ICs.  The router did a good job on it.  An afternoon to tweak the rules,
> and
> 30 minutes to clean up afterwards.
> If you have lots of replicated circuitry with parallel, ordered busses,
> 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
> 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
> designs?
> > 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
> setting
> > it up properly. What do you people do?
> >
> > Tim Fifield
> >

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