FreeLists / si-list / [SI-LIST] Re: Paper on BGA crosstalk and power system

[Stefan Ludwig <ludwig@xxxxxxxxxxxxxxxxx>]

Hi Cliff & Steve,

I have seen the webcast and in that, Dr. Johnson mentioned that Altera 
didn't have a fast vs. slow setting for the slew rate. Therefore, they 
used fast on Xilinx, but had to live with the even faster edge rate of 
Altera's devices.

Maybe a fairer comparison would have been 8mA A vs. 12mA X, i.e., 
compensate faster slew rate of A with higher drive strength of X, but 
I'm not sure that would have yielded a comparable result.

Just my opinion.

Stefan

Clifford van Dyk wrote:

>Hi Mark
>A very interesting paper indeed. While not having seen the webcast, I 
>assume that the content is more or less contained within the paper. 
>While I do not see myself in the same league as other S.I. experts in 
>the forum, hopefully my opinion is in some way useful. I would be 
>interested to know the following:
>
>The final simulations show what looks to me like a 6 time greater 
>crosstalk in the Altera package. This was done under the assumption that 
>di/dt was the same for both devices. The measured results (a ratio of 
>4.5:1) were made with the Altera drivers being significantly stronger 
>than the Xilinx drivers. I would therefore have expected the simulated 
>ratio to be less that 4.5:1, rather than the ca. 6:1 that seems to be 
>indicated on figure 21. Why do you think this discrepancy exists?
>
>Also, it may have been more useful to perform the origional measurements 
>with equivalent drive strengths (measured risetimes, rather than "8mA" 
>vs. "8mA fast", which was by your own admission, misleading) to get a 
>more apples-to-apples measurement. Do you agree?
>
>Nevertheless, very interesting! Thank you for sharing.
>
>Kind regards,
>Clifford
>
>Mark Alexander wrote:
>
>  
>
>>Hey all,
>>Some of you may have already attended this, but I wanted to draw your 
>>attention to a WebCast seminar and accompanying paper that was released 
>>yesterday.  The topic is a joint study by Xilinx and SigCon (Howard 
>>Johnson) of crosstalk and power system noise in FPGA systems.
>>
>>The paper:
>>http://www.xilinx.com/products/virtex4/pdfs/BGA_Crosstalk.pdf
>>
>>The archived WebCast (might not be available until tomorrow):
>>http://www.xilinx.com/events/webcasts/tol/01feb05.htm#3
>>
>>The WebCast is a full hour with Q&A at the end; the paper /seems /long 
>>but is actually pretty easy to read.  I especially like Howard's 
>>explanation of the crosstalk model of power system noise and why it's 
>>appropriate to the large BGA scenario.
>>
>>I'd be very interested to hear feedback from people on the list -- 
>>factors we didn't consider, overall usefulness of the information 
>>presented, ideas for future studies on the same measurement platform. 
>>
>>Thanks!
>>mark
>>
>>
>>
>>
>> 
>>
>>    
>>
>
>
>NOTICE: Please note that this email, and the contents thereof, 
>are subject to the standard Peralex email disclaimer, which may 
>be found at: http://www.peralex.com/disclaimer.html
>
>If you cannot access the disclaimer through the URL attached 
> and you wish to receive a copy thereof please send 
> an email to email@xxxxxxxxxxx
>
>
>------------------------------------------------------------------
>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:
>http://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:     
>               http://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
>  
>
>
>  
>

-- 

Ludwig Systems Engineering         Consulting - Design - Implementation
WWW: www.ludwigsystems.com         System Architectures - FPGAs - PCBs
Ph/Fx: +41-43-355-58-73/74         Hardware - Firmware - Software

------------------------------------------------------------------
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:
http://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:     
                http://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