No, it is really the skew between two different pairs. The interpair skew is 0.5mm between P and N. The exact relevant paragraph in the PICMG 3.0 specification is "6.2.3.2 Base and Fabric Interface requirements" Daniel "Leonard Dieguez" <ldieguez@xxxxxxxxxx> 28/11/2006 18:21 To: Daniel PERON/FR/ALCATEL@ALCATEL cc: Subject: RE: [SI-LIST] PICMG3.1 : is length matching really necessary? I think that they are talking about interpair skew between the P and the N Leonard. -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Daniel.Peron@xxxxxxxxxx Sent: Thursday, November 23, 2006 8:05 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] PICMG3.1 : is length matching really necessary? Hi all, In PICMG3.0, there is a requirement for length matching between the pairs of a fabric interface channel : 2.54mm max. Even for 10G backplane Ethernet type applications (PICMG3.1 / 10GBase-CX4) this seems exagerated, as data are aligned at PCS level. --> in 802.3 clause 48.2.4.2.2 there is a skew budget table, which allocates 2UI (=2x320ps) for PCB (board) skew and 18UI for the transmission medium (backplane) skew. Is my understanding of the standard correct or do I miss something? Thanks for your help. Regards. Daniel Peron ------------------------------------------------------------------ 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