[SI-LIST] Re: DesignCon Papers
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- Date: Tue, 08 Feb 2005 15:49:26 -0500
Patrick,
Interestingly enough, Chris Cheng is not a consultant. He is a designer
of big iron stprage systems at 3 Pardata. Before that he had his hand
in the modeling and simulation effort for the Itanium frontside bus at
Intel. Before that, he tormented engineers at Sun for a living.
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed is the registered service mark of
Teraspeed Consulting Group LLC
Patrick Zilaro wrote:
>Guys,
>
>Chris Cheng purposely acts like this to gain notoriety for the purpose =
>of
>promoting his consulting services.
>
>Please ignore him. The more you publicly "take offense, etc.", the more =
>he
>is getting exactly what he wants.
>
>Regards,
>
>Patrick
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
>On
>Behalf Of Paul Taddonio
>Sent: Tuesday, February 08, 2005 12:13 PM
>To: Chris.Cheng@xxxxxxxxxxxx; 'silist'
>Subject: [SI-LIST] Re: DesignCon Papers
>
>I object to the tone and content of this posting.
>
>Paul Taddonio
>
>----- Original Message -----=20
>From: "Chris Cheng" <Chris.Cheng@xxxxxxxxxxxx>
>To: "'silist'" <si-list@xxxxxxxxxxxxx>
>Sent: Tuesday, February 08, 2005 2:25 PM
>Subject: [SI-LIST] Re: DesignCon Papers
>
>
>
>
>>Would you care to take the Chris Cheng challenge ?
>>
>>If you don't believe in PI problem. Take out all the PLLVDD filters
>>
>>
>(forget
>
>
>>about those crazy output VDD filter, which is questionable) on your
>>
>>
>favorite
>
>
>>FPGA or SerDes. Let's see how many of them fail mysteriously in the =
>>
>>
>field
>or
>
>
>>just fall off on its face on the tester. And how long you can keep =
>>
>>
>your
>job
>
>
>>as a consultant. I have many of the hotshot PLL designers, system
>>
>>
>designers
>
>
>>challenging me on this. If you think I am an ass in Si-list, you =
>>
>>
>should
>ask
>
>
>>those people what kind of ass I am when I start taunting them when =
>>
>>
>they
>come
>
>
>>back to apologize. Ask Ray and Larry's old boss for example.
>>
>>But seriously, ask youself this question, in your 15+ year of =
>>
>>
>experience,
>
>
>>how many times you have to design a 100W+ and >1GHz core chip and =
>>
>>
>package?
>
>
>>Of those chips, how many of them has to have these superwide (288 bit
>>
>>
>width
>
>
>>per bus) FSB on top of $ BSB with 18+ layer boards ? Like I said =
>>
>>
>before,
>if
>
>
>>you are not ready to run with the big boys, stay with the crowd. The =
>>
>>
>sad
>
>
>>thing is, I can count with one hand how many of those companies can =
>>
>>
>still
>
>
>>afford to it and my thinking is it will be even less in a few years.
>>
>>-----Original Message-----
>>From: Robert Sefton [mailto:rsefton@xxxxxxxxxxxxx]
>>Sent: Monday, February 07, 2005 9:40 PM
>>To: 'silist'
>>Subject: [SI-LIST] Re: DesignCon Papers
>>
>>
>>Dear list, especially the power integrity experts and pioneers at Sun,
>>Teraspeed, et al -
>>
>>I've been a list member for more than five years now - rarely
>>
>>
>contributing,
>
>
>>but religiously monitoring the dialogue. In the 15+ years I've been in
>>
>>
>this
>
>
>>business I've been responsible for or at least been involved in dozens =
>>
>>
>of
>
>
>>large PCB designs. Over all of those designs I've seen maybe 4-5 =
>>
>>
>signal
>
>
>>integrity problems (where operation was affected), but I have never, =
>>
>>
>ever
>
>
>>seen a power integrity problem. Virtually all of these designs have
>>
>>
>included
>
>
>>at least one FPGA, a processor, and SRAM and/or SDRAM. And several =
>>
>>
>have
>
>
>>included FPGAs plus ICs dissipating 20+ watts with SPI-4.2, SerDes, =
>>
>>
>DDR,
>and
>
>
>>other high speed interfaces.
>>
>>I'm a consultant, and I primarily work with small start-up companies =
>>
>>
>that
>
>
>>have no budget and no inclination for SI tools. (They'll spend many =
>>
>>
>$100Ks
>
>
>>or even $1Ms on IC tools, but won't spend a dime on PCB tools other =
>>
>>
>than
>
>
>>schematic entry and layout.) Probably half of the boards I've been
>>
>>
>involved
>
>
>>with are prototype builds where schedule is paramount. With these I =
>>
>>
>can
>
>
>>rarely exert enough control to get the layout exactly like I want, and
>>
>>
>often
>
>
>>the boards go out with serious reservations on my part. I always try =
>>
>>
>to
>
>
>>observe the prevailing guidelines expressed here and elsewhere, but =
>>
>>
>I've
>
>
>>seen boards go out with barely any copper left in the "planes" beneath
>>
>>
>large
>
>
>>power-hungry BGA parts due to poor via placement and large anti-pads. =
>>
>>
>I
>
>
>>recently saw a board come back where a large Virtex-II FPGA would not
>>configure. It was traced down to the fact that the core power islands
>>
>>
>under
>
>
>>the BGA were were so sliced up that they were not connected to the =
>>
>>
>core
>
>
>>power VRM. The swiss cheese core power "plane" was re-connected to the
>>
>>
>+1.5V
>
>
>>supply with a 4" blue wire through one via on the bottom of the board.
>>
>>
>Guess
>
>
>>what - it worked like a champ.
>>
>>I'm not trying to be an ass here (I'll leave that to Chris C. :`)), =
>>
>>
>but
>I'm
>
>
>>really beginning to question the need for some or even most of the
>>theoretical PI analyses espoused here. I can't believe that luck has =
>>
>>
>made
>
>
>>all of my boards work over the years, despite not having access to SI =
>>
>>
>or
>PI
>
>
>>tools of any kind. What I really think is going on is that there are =
>>
>>
>very
>
>
>>few designs that need the ultra-low-mOhm, highly-simulated, and
>>highly-engineered power distribution methodologies that have been
>>
>>
>discussed
>
>
>>here recently. I'll be damned if I can make a board NOT work due to =
>>
>>
>how
>
>
>>power is distributed.
>>
>>In the PI discussions on the SI-list I almost never hear power/current
>>levels discussed. I'm sure that Sun cranks out boards with processor =
>>
>>
>ICs
>or
>
>
>>modules that draw 10s of Amps of core power, where detailed analysis =
>>
>>
>of
>the
>
>
>>PDS is critical. But what about us mortals who design run-of-the-mill =
>>
>>
>FPGA
>+
>
>
>>PowerPC + MAC, etc., type of boards? As I said, despite some brutally =
>>
>>
>bad
>
>
>>layouts, I have NEVER had a problem related to power distribution.
>>
>>I have two requests to the list:
>>
>>1. When espousing SI and/or PI practices, please be as specific as
>>
>>
>possible
>
>
>>about when these practices are warranted, and more importantly, when =
>>
>>
>they
>
>
>>are not.
>>
>>2. I would LOVE to hear more detailed reports from the trenches (i.e. =
>>
>>
>war
>
>
>>stories) about SI and PI problems that were actually seen on real =
>>
>>
>boards
>
>
>>(not in simulation), and how they were fixed. This is something that =
>>
>>
>is
>
>
>>almost NEVER discussed amongst the regulars here.
>>
>>I have a strong sense that non-experts (like me) who monitor this list =
>>
>>
>are
>
>
>>buying into methods that may not apply to their designs and are =
>>
>>
>therefore
>
>
>>over-engineering (one of my least favorite things - I prefer to
>>under-engineer and get away with it).
>>
>>All comments are welcome.
>>
>>Best regards,
>>Bob Sefton
>>
>>
>>
>>------------------------------------------------------------------
>>To unsubscribe from si-list:
>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>>
>>or to administer your membership from a web page, go to:
>>//www.freelists.org/webpage/si-list
>>
>>For help:
>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>>
>>List FAQ wiki page is located at:
>> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>>
>>List technical documents are available at:
>> http://www.si-list.org
>>
>>List archives are viewable at:
>>//www.freelists.org/archives/si-list
>>or at our remote archives:
>>http://groups.yahoo.com/group/si-list/messages
>>Old (prior to June 6, 2001) list archives are viewable at:
>> http://www.qsl.net/wb6tpu
>>
>>------------------------------------------------------------------
>>To unsubscribe from si-list:
>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>>
>>or to administer your membership from a web page, go to:
>>//www.freelists.org/webpage/si-list
>>
>>For help:
>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>>
>>List FAQ wiki page is located at:
>> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>>
>>List technical documents are available at:
>> http://www.si-list.org
>>
>>List archives are viewable at:
>>//www.freelists.org/archives/si-list
>>or at our remote archives:
>>http://groups.yahoo.com/group/si-list/messages
>>Old (prior to June 6, 2001) list archives are viewable at:
>> http://www.qsl.net/wb6tpu
>>
>>
>>
>>
>>
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>//www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at: =20
> //www.freelists.org/archives/si-list
>or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
> =20
>
>
>
>
>------------------------------------------------------------------
>To unsubscribe from si-list:
>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
>or to administer your membership from a web page, go to:
>//www.freelists.org/webpage/si-list
>
>For help:
>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>List FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at:
> //www.freelists.org/archives/si-list
>or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
>Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>
>
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
