Tprop is the propogation delay. Td is the velocity of the wave in the microstrip Hence trace length = Tprop/Td = 2000/175 inch = 11 inch. What is missing is your rise time which will give your electrical length to compare against your trace length. This will also give your max. trace length where you won't have to worry about reflection. Anything above that requires termination of some sort to prevent reflections --- On Wed 05/22, Brahim Koudssi wrote: Hello SI Group, Please help me understand the definition of Tprop and how to calculate the Max. trace length? PCIX at fclk=133 mhz Tprop=2ns Td= 175ps/in Thanks, Brahim Koudssi ------------------------------------------------------------------ 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 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 ------------------------------------------------ Join Excite! - http://www.excite.com The most personalized portal on the Web! ------------------------------------------------------------------ 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 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