steve weir wrote: >1) Why three big power planes if they do not form cavities with logic >ground? If this is a DC problem then apply a DC solution. > And from the DC perspective, if 3 planes are needed on the supply side to provide sufficient current, then three ground planes would also be needed to complete the circuit. Nasty stackup indeed. Ivor, you need two more layers. May I suggest (depending on your signals of course): 1. Component/signal 2. Ground 3. Power 4. Signal 5. Signal 6. Power 7. Ground 8. Signal 9. Signal 10. Power 11. Ground 12. Component/Signal Alan ------------------------------------------------------------------ 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