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Technology Stocks : Rambus (RMBS) - Eagle or Penguin -- Ignore unavailable to you. Want to Upgrade?

To: wily who wrote (34336)	11/12/1999 2:43:00 PM
From: John Walliker	Respond to of 93625

wily, Please thank Paul DeMone for his detailed response. The following documents from the Rambus and Intel web sites should answer his questions. This Rambus document describes in detail the use of narrowed tracks to maintain constant effective trace impedance: RIMMDsgnGuide.pdf The following Rambus document includes description of time domain reflectrometry fixtures: RIMMModSpec051.pdf From the Intel website pcbtest.pdf and pcd_pres399.pdf discuss TDR testing in great detail. We agree that there are significant time of flight delays. What I disagreed with was the analysis that suggested that device input capacitances would add to those delays in any significant way. In particular, the use of a 50 ohm system for that calculation made the effect of uncompensated loading greater than it would have been at 28 ohms. I think the documents that I have referenced do show that Rambus use track narrowing to achieve the compensation that I described. If measurements are done with a high enough bandwidth, then of course a TDR will detect a rise in impedance just before each device, a drop at the device and a rise again just after before returning to the nominal value. However, within the bandwidth that Rambus uses, those irregularities will be within the bus impedance specification. Thank you again for taking the time to respond. John