Ray, That's about what I remember how we did it before I left. And for package resonance below 100MHz, the external PCB bypassing analysis can use the simplified models. But the core FUB units and clock trunk needs the transistor scale models to estimate the negative feedback on the current as the supply collasp. That's another level of detail the board designer doesn't need to know. -----Original Message----- From: Ray Anderson To: si-list@xxxxxxxxxxxxx Sent: 12/30/2004 10:43 AM Subject: [SI-LIST] Re: Article discussion on bad packages Chris Cheng wrote: >Istvan, > >I would also like to ask the questions for one last time : >a) Does SUN use IBIS or SPICE to analyze its critical IO or CPU core power >distribution ? >b) Were you actually responsible to work on the CPU core power distribution >analysis for your company ? >I will be waiting till hell freezes over. > > > One way I've done core PDN simulations on processors in the past was to initially have the silicon design guys run time domain transistor level core simulations. These involved millions of transistor and took way too long to run. From the time domain I vs T results of those simulations a behavioral model consisting of PWL current sources or PWL voltage controlled resistances was developed. We then utilized those behavioral models to characterize the time domain response of the core PDN's. It was always instructive to look at the p-p current excursions at the silicon, at various points in the package and finally at the PCB level to visualize the effects of the on chip, on package and PCB level decoupling networks. The behavioral models ran in seconds or minutes as compared to the transistor level models they were derived from which executed in terms of days or weeks. -Ray Anderson Senior Signal Integrity Staff Engineer Xilinx Inc. ------------------------------------------------------------------ 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