[SI-LIST] Re: DDRAM BUS Testing

  • From: "Jim Antonellis" <janton@xxxxxxxxxxxx>
  • To: <hmurray@xxxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Fri, 4 Aug 2006 10:19:47 -0400

Hi Hal,

Agreeing with all of the previous points in regards to locale, i.e.
Vdd-core, Vdd-io on die, pkg and PCB, I would like to share a
"war story"....

At one point, in our lab, I measured a system (many layers, many decaps)
plane and tracked the system performance (logical operation) and the
plane noise (diff plane measurements at decap site) as I removed caps 
on a particular rail. The local noise (as measured diff at the decap) 
did increase with the removal of decaps but interestingly the system
did not "fail" (functional errors, I did not track the jitter or timing)
until almost all of the decaps were removed. We were extrememly over
zealous with the decaps.

In closing, I do not assert that the experiment was well controlled,
but at a gross level it confirmed that at a local level the decaps
were doing something. If I have the time I'll dig out the report
(I did document the work) and can send it to interested parties
off-line.

Jim

-
Jim Antonellis   janton@xxxxxxxxxxxx
Broadcom Corp    www.broadcom.com
Office: 978.689.1669 
Cell: 978.618.4745

This message and any attachments are Confidential and may be Legally
Privileged. It is intended solely for the addressee. If you are not 
the intended recipient, please delete this message from your system 
and notify us immediately. Any dis-closure, copying, distribution or 
action taken or omitted to be taken by an unintended recipient in 
reliance on this message is prohibited and may be unlawful.
 
 
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Hal Murray
Sent: Friday, August 04, 2006 8:49 AM
To: si-list@xxxxxxxxxxxxx
Cc: hmurray@xxxxxxxxxxxxxxx
Subject: [SI-LIST] Re: DDRAM BUS Testing


> Ihsan, in most systems we have many capacitors.  In many of the more 
> expensive systems, we also tend to have relatively thin power cavities 
> tying capacitors and loads together.  So, removing one cap for the 
> sake of measurement yields a tolerable error that we can pretty much 
> calibrate out once we consider the capacitor and IC distribution, and 
> the composition of the plane cavity(s).

How often do people get in trouble because the manufacturing line misses a
bypass cap or several?  (I don't remember any war stories on that topic.)

Is there any simple way to check for that sort of thing in a production
testing environment?  I'd expect the system to keep working, but with
reduced noise margins.  That is it will work well enough to pass all the
tests but might fail occasionally after it gets to the customer.

--

The suespammers.org mail server is located in California.  So are all my
other mailboxes.  Please do not send unsolicited bulk e-mail or unsolicited
commercial e-mail to my suespammers.org address or any of my other
addresses.
These are my opinions, not necessarily my employer's.  I hate spam.



------------------------------------------------------------------
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
  





------------------------------------------------------------------
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
  

Other related posts: