I disagree. No one should be surprised. I have said many times, there is never a need for fancy decoupling scheme on PCB for properly design processor and package. Nothing should be need for >100MHz core noise and signal return is a case of reference plane management (does that sound like a broken record yet ?) Call me cynical but most of the so call power distribution papers, book authors never have a complete picture of the power distribution scheme. They either built some fancy plane model of a pcb or some complicated package model and "discover" these crazy resonance here or there and proclaimed "there, we've got a problem on this package or pcb, I see this huge peak at xxxM or G/Hz". What they don't know is the effect of on die power grid and decoupling effect which will significantly change the resonance pattern and frequencies. Anyone who really have done a complete analysis including on die power grid will be bounded by their own company gag rule to not telling you what they are. I always call that "core competency". Either you know it or you don't. Couple this with overly eager PCB vendor who are pushing BC or cap vendors trying to sell you expensive caps or even CAD vendor who want to get your PO for that "plane analyzer tool that can hunt for xxxMHz resonance in your PCB", you've got an urban legend that feeds a whole industry of consultants, vendor and tools that provide a solution that is looking for a problem. I do have to agree, as Steve Weir pointed out previously, if you have a poorly design chip and package, you need a hell of a lot of decoupling and BC planes to fix it at the system level. But two wrong does not make one right in my book. BTW, I ran couple of those power analysis groups in a server and a PC processor company. I hope you will trust what I am saying. -----Original Message----- From: Charles Grasso [mailto:cgrassosprint1@xxxxxxxxxxxxx] Sent: Monday, January 12, 2004 6:20 PM To: martin@xxxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Power Supply Distribution/Filtering/Decoupling Guide Thanks for the info Martin. I learn more from things that work - but shouldn't.!! -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Martin Euredjian Sent: Monday, January 12, 2004 5:08 PM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Power Supply Distribution/Filtering/Decoupling Guide So... I just got one of the new Intel D875PBZ motherboards (3.6GHz, 800MHz FSB, etc.). In looking at it, one of the things that caught my eye immediatlely was wasn't there. I was expecting lots of decoupling capacitors, particularly surrounding certain chips. To my surprise, the design has absolutely no components on the bottom and an (appartent) handful of decouplers on the top layer. With all the talk and controversy on this forum, application notes, papers and books describing gargantuan capacitor trees as a requirement for good signal integrity, reduce RFI, etc. it's always been a surprise to run across product after product that does not seem to fit the proposed model very well. Am I missing something fundamental here? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Martin Euredjian eCinema Systems, Inc. voice: 661-305-9320 fax: 661-775-4876 martin@xxxxxxxxxxxxxx ecinema@xxxxxxxx www.ecinemasys.com ------------------------------------------------------------------ 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 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 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 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