Chris, No, your thinking is not sound. The margins on DDR busses are generally low and require careful consideration of in-bus crosstalk. Crosstalk within a bus on the data lines can be looked at in two ways. #1) Crosstalk can be seen as noise injected from one signal into another. This noise then adds to the instantaneous voltage on the victim signal. This upset can look like additional positive or negative overshoot, it can look like IEEE undershoot, in that it it supresses the rising edge transition, or it can cause jitter in the waveform. All of these can be detremental on bus operation. First, jitter translates into a reduction of timing margin. Second, excessive overshoot can cause receiver voltage to extend beyond the maximum operating range of the device. This overshoot operation can cause eventual distruction of the input through electromigration. #2) Crosstalk can be seen as a dynamic impedance and propagation velocity change on the victim line. This dynamic change, the magnitude is dependent upon the magnitude of the crosstalk, and also commonly called the even and odd model coupled transmission line characteristics, is another way of looking at why excess jitter, overshoot and IEEE undershoot occur in coupled transmission lines. Again, this can be extreme enough to break bus operating margins for both voltage and timing. Finally, crosstalk from DQ to QDS lines can be catestrophic, since noise injected can rise to the extreme of causing false strobe transitions at the receivers. Early DDR chipsets had to be redesigned due to DQ signals being routed adjacent to DQS signals inside of packages, causing bus failures. I hope this description helps you. regards, scott Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax (503) 750-6481 Cellular http://www.teraspeed.com Teraspeed is the registered service mark of Teraspeed Consulting Group LLC ------------------------------------------------------------------ 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