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

2002-01-22 Thread ga


Hi all,

I agree with Remco, you always want to change something after the
autorouter has finished. The DWIT command (do what I'm thinking) still
has not been implemented    :-)

But I want to speak in favour of Swiss cheese, not only because of its
excellent taste.
It is true that an autorouter like e.g. SPECCTRA will not generate these
parallel, evenly spaced bus structures on dense boards that you find on
many hand-routed boards (especially PC motherboards, where you have all the
space of the world for routing), which results in far less vias than what
an autorouter will produce. But is this really desirable? There are pros
and cons for both approaches. In very high speed design, every via creates
a tiny reflection on the signal that may be intolerable with signal
frequencies of several 100 MHz and above, whereas with frequencies below
100 MHz this will probably not be a critical issue. On the other hand,
parallel bus structures can cause crosstalk problems hard to debug, which
will simply not be there if the board was autorouted like Swiss cheese.
Critical signals like fast clock traces or fast line interfaces I always
route manually before invoking the autorouter. Of course also these signals
can be routed satisfactory by a good autorouter, but it is necessary to
define very precise rules for every critical signal and having purchased
the router option needed to enable it to follow these rules (FST option
with SPECCTRA, this option being about the same price as the complete
router package including all other options).

Gisbert Auge
N.A.T. GmbH



   
   
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Dear Matt,

Normally I only route the boards by hand (4  6 layers) , my expierence
with
autorouting utillities (not only Protel) is that you still want to change
tracks which you don't like so you will wind up re routing the whole board
:)

The only thing i sometimes use the autorouter for is routing the databus on
the pcb, only if there aren't any other tracks routed or else you get your
swiss cheese...

Remco van den Heuvel.
Hardware Engineer.

Please feel welcome to visit our website at:
http://www.fusionelectronics.org

---
Willem Alexanderweg 87, NL-3945 CH Cothen
email: [EMAIL PROTECTED]
tel: (+31)343590600
fax (+31)343578599
---


- Original Message -
From: Matt Polak [EMAIL PROTECTED]
To: Protel EDA Forum [EMAIL PROTECTED]
Sent: Monday, January 21, 2002 4:51 PM
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

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

2002-01-22 Thread Jon Elson



 At 10:51 AM 1/21/2002 -0500, Matt Polak wrote:

  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.

I typically do 100 in^2 4 layer designs, with a few 6 layer.  I also do other
ones that range from 4 to 30 in^2, 2 and 4 layer.  I usually let the autorouter

do as much as possible on the multilayer boards, then clean up the mess and
route the remaining traces.  Rediculous routes that run all around the
perimiter
of the board to go only a short distance are common, even with 6 layers.
Maybe my route setup is not correct for the job.  I have done a number
of boards that had a wild mixture of pad pitches, which makes the router's
job a lot harder.

  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.


I don't know if letting the autorouter start on this and then fix it up
manually
is a smart way to go.  I guess I just keep hoping the autorouter will do a
great
job someday, but the fixup often takes a while.  If you have a lot of
differential
pairs, terminated lines and mandated trace delays, then maybe a total manual
route is the way to go.  Otherwise, route all critical stuff manually first,
then
let the autorouter complete it.

Jon

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

2002-01-21 Thread Abd ul-Rahman Lomax

At 10:51 AM 1/21/2002 -0500, Matt Polak wrote:

 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.

I don't know about the majority, many of us are doing simple designs. We do 
both, but the vast majority of our designs are hand-routed. Sometimes, 
perhaps, we should be autorouting these boards, but we have a preference

 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.

It may be some time before you see an autorouter that will be fully 
satisfactory. At the present time, autorouters are especially good with 
boards that are complex in terms of numbers of connections but do not 
require space and layer optimization. In other words, they have room. 
Perhaps a company wants to make a test fixture, it has lots of parts but 
only a few are going to be made. In that case, the improved layout quality 
possible with hand routing is not cost-effective.

It's not just a matter of aesthetics. Good manual routing will, given the 
present state of the art, typically have shorter track lengths and fewer 
vias. As autorouter technology advances, I expect this advantage to be 
lost. How long it will take, I do not know.

 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?

Probably. But Protel's current router, under some conditions, can make 
fairly pretty boards. And that board may have been routed, say, with 
Specctra, which can cost, by itself, substantially more than the whole 
Protel suite.

 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.

I'll try to pull something out of my head.

I tend to place and route at the same time, placing components that seem to 
naturally go together -- perhaps they share a bus or busses -- and making 
the placement as tight as might be reasonable. At least I do enough 
routing, if any is necessary, to satisfy myself that this section of the 
board is going to route properly and efficiently. I might reassign gates or 
I/O ports at this time. These sections are then arranged in the board 
space. As a result, you might see, with one of my designs, tight space and 
empty space.

This is because tighter, in general, is better. One can always, if it makes 
a difference, spread parts out, though usually it is not worth the effort. 
But making a design tighter can be anywhere from time-consuming to 
impossible. So aim tight. It's also typically better, when done 
intelligently, from a noise perspective.

[EMAIL PROTECTED]
Abdulrahman Lomax
Easthampton, Massachusetts USA

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

2002-01-21 Thread John Whittaker

Matt
I am a circuit/system designer who is is self-taught on PCB design.  I
design my own pcb's because I design portable electronics and the
flexibility of placing the components at the time I'm designing the
electronic package, etc. gives me some incredibly efficient packaging
results.  I only design portables.  I recently used Protel Successfully to
route a Pentium-III Portable mainboard with 12 layers and several BGA
devices.  The first spin of the board booted Windows.  If I were to contract
out to a pure PCB designer, then I would have much less flexibility in the
overall design, electronic, mechanical, and interconnect.  SO I do it myself
first, then contract out for production once I get the design up and
running.

I have had some serious battles with Protel software.   But I have set up
and run the autorouter, and once when I sent a board out and had the
SPECCTRA autorouter run, the difference between the two was not as great as
I would have guessed.  Remember, that's from a layman in terms of PCB
routing efficiency.

Personally, I am going to give the next release of Protel a long, hard look.
I have resisted the move to PADS because of the expense and learning curve -
I have been using Protel for several years.

-Original Message-
From: Matt Polak [mailto:[EMAIL PROTECTED]]
Sent: Monday, January 21, 2002 9:51 AM
To: Protel EDA Forum
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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Re: [PEDA] Autorouting or manual routing, or both?

2002-01-21 Thread Clive . Broome





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
like
terminations, bypassing, planes, routing impedance etc.



___

Clive Broome
IDT Sydney Design CentrePh: +61 2 9763 3513
8 Bayswater Dr, HomebushFax:+61 2 9763 3409
Sydney,  NSW, 2127  Email:[EMAIL PROTECTED]
Australia

___








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

2002-01-21 Thread Remco v/d Heuvel

Dear Matt,

Normally I only route the boards by hand (4  6 layers) , my expierence with
autorouting utillities (not only Protel) is that you still want to change
tracks which you don't like so you will wind up re routing the whole board
:)

The only thing i sometimes use the autorouter for is routing the databus on
the pcb, only if there aren't any other tracks routed or else you get your
swiss cheese...

Remco van den Heuvel.
Hardware Engineer.

Please feel welcome to visit our website at:
http://www.fusionelectronics.org

---
Willem Alexanderweg 87, NL-3945 CH Cothen
email: [EMAIL PROTECTED]
tel: (+31)343590600
fax (+31)343578599
---


- Original Message -
From: Matt Polak [EMAIL PROTECTED]
To: Protel EDA Forum [EMAIL PROTECTED]
Sent: Monday, January 21, 2002 4:51 PM
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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