I can't read the minds of my competitors who designed the connectors you mentioned (although I CAN read their Patents...). But I might be able to add some insight based on some of our connector designs. For optimal electrical performance, it is usually best to position a differential pair horizontally in a connector. There are some exceptions, but not many. But there are often non-electrical reasons that can make a vertical pairing attractive. Two good examples are signal density and connector cost. In some cases, the non-electrical benefits of a vertical paring can off set any electrical penalties. Also, some of the skew inherent in a vertical pairing can be compensated for in the pcb. Some can also be compensated within the connector itself, by judicious use of materials and geometries. The bottom line is that each particular application has its own electrical requirements, and in many cases, a vertical pair is "good enough". Julian Ferry High Speed Engineering Manager Samtec, Inc Mechanicsburg, PA -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Stephen Greenhalgh Sent: Thursday, January 05, 2006 6:13 AM To: Si-List (E-mail) Subject: [SI-LIST] differential pairs on backplane connectors When using standard pin matrix backplane connectors (for example, 2mm hard metric), the conventional wisdom was to assign two adjacent pins in the same row for a differential pair. This meant that the right angle (daughter board) connections were of equal length and geometry. However, the newer connectors, designed specifically for differential pairs (for example, FCI Airmax VS, Amphenol GcX or ERNI ERmet ZD) use pairs of pins in the same column. This seems surprising, since it appears to mean that there is an inherent imbalance between the two connections. Perhaps this is taken into account in the connector design? Can anyone provide an explanation or clarification, please? Stephen Greenhalgh ------------------------------------------------------------------ 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