A very good website that deals with high speed design is
www.signalintegrity.com. It is
hosted by Dr Howard Johnston and has articles on specific aspects of PCB design
terminations, bypassing, planes, routing impedance etc.


Clive Broome
IDT Sydney Design Centre        Ph:         +61 2 9763 3513
8 Bayswater Dr, Homebush        Fax:        +61 2 9763 3409
Sydney,  NSW, 2127              Email:[EMAIL PROTECTED]


"Matt Polak" <[EMAIL PROTECTED]> on 01/22/2002 01:51:20 AM

Please respond to "Protel EDA Forum" <[EMAIL PROTECTED]>

To:   "Protel EDA Forum" <[EMAIL PROTECTED]>
cc:    (bcc: Clive Broome/sdc)

Subject:  [PEDA] Autorouting or manual routing, or both?

     Hey folks,

     It seems that a majority of you are doing some very dense, high-speed
layouts with 4-6 layers being quite a common occurrence. I'm just wondering
how much you typically route by hand, and how much you let the auto-router
whack away at.

     Being primarily self-taught in the ways of Protel, and with the help of a
few 'older school' engineer friends here and there, I've done a number of
successful design layouts thus far, but these have been relatively simple 2
and 4 layer designs without many small-pitch/high pin-count devices. I'm
moving more towards laying out more high-speed designs in the near future
where a lot of stuff needs to be fit into a small place, and all connect
together without traces and vias meandering all over.

     When I look at sample six layer boards (such as the 5407 EVM reference
design Motorola has released) the bussing and interconnects are extremely
elegant and efficient in appearance. For fun, I unrouted the 5407 board and
then let the autorouter chew on it. It immediately made 'via swiss-cheese'
out of the board and created little more than a large mess. I'm GUESSING
quite a bit of these sort of designs are laid out by hand, or at least
pre-routed to give the auto-router a sense of direction?

     Can anyone offer some basic pointers to getting started into planning and
laying out PCBs for multi-layer, high-speed designs such as these? I have
no idea where one would really even start with something like this. It
seems most of the important knowledge gets passed directly from engineer to
engineer; there are certainly no university classes (that I know of,
anyway) that teach you how to lay out a dense, 6 layer board. :/ I
appreciate the patience and wisdom of those who remember once being where I
am now, who are willing to take the time to pass some of the tips and
tricks down the engineering family tree.

     Thanks again for any pointers anyone can provide (either through the list,
or privately.)

Best regards,
-- Matt

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