Hi roy: You can go to www.appwave.com/download and get a free tool called TxLine that will help you design your diff lines given the dielectric constant and thickness of the board.=20 If you have problems with this, let me know. Regards, MikeH -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Luc Durand Sent: Wednesday, November 16, 2005 6:45 AM To: roymesi@xxxxxxxxx; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: PCI-E, Zdiff and Er Hello Roy, I have not read the PCI-E spec but I am surprised it would ask for specific track widths/distances if they do not specify the dialectric as well since woth are related. My guess is the spec asks for a Zohms of 100 ohms and it is up to you to calculate the proper width/distance by the dialectric you wish to use. Regards -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Roy M Sent: Wednesday, November 16, 2005 3:51 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] PCI-E, Zdiff and Er Hi Everyone, I'm designing a PCI-E board and trying to figure out what the Er (dielectric constant) should be in order to achieve the 5-5-5 width-space demand for PCI-E and the Zdiff=3D3D100ohm (i found out that 5-5-5 is the demand for PCI-E traces - could anyone confirm that???). i tried to find in the internet something related to Er for PCI-E but couldn't find anything. I did find though that the standard width of the add on card is 63mil (1.6mm), but regarding the Er - zippo. What kind of substrate is better to achieve the 5-5-5? (i mean FR4 of Er=3D3D 4.2 or maybe something else...) Maybe somone here designed other space-width ratio and achieved Zdiff=3D3D100ohm? because i didn't succeed... what i got for Er=3D3D3.8 = was 4-8-4 and not 5-5-5 Thanks, Roy ------------------------------------------------------------------ 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: =3D20 //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 =3D20 ------------------------------------------------------------------ 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: =20 //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 =20 ------------------------------------------------------------------ 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