If you really can't build test cards ( ask your management what is worse a few $ on test cards or late shipment of product, I know which I would choose), then the DDR2 reference DIMM modules do have probing points as close to the BGA pad as they can get. I would follow the same practice and simulate with the probing you envisage using, and then correlate this with your measured results. Regards John arsenault, brian wrote: >Folks... > >I'm looking for some suggestions and ideas on how to perform SI measurements >and correlate them to simulations when you don't have access to the receiver >pin. > >For example, one of our designs is looking at back-to-back mounting of DDR-2 >memory chips, and based on the spacing of the board, the vias close to the >receivers (the RAM's, when a read operation takes place) will not be >accessible. The same thing would apply to probing signals at a receiver >that is using blind and buried vias. > >Traditionally, all of our technology has utilized only through-vias, and we >have been able to probe directly on the pins of the receivers if a via was >not located very close by. As we're moving forward, it's apparent that we >need to find a better way to both show the designer that his/her design will >work, and for the SI group to correlate their simulations to measurements. > >I'm aware that building a test card to validate the buffers is one way to >go, but in these times, we are trying to minimize extra costs. > >Thanks... > >Brian > > >Brian Arsenault >Principal HW Engineer >EMC Corporation >Hopkinton, MA > > > >------------------------------------------------------------------ >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