Re: [SI-LIST] : PCI Bus problem (an interesting one)

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From: Michael Nudelman (mnudelman@tellium.com)
Date: Mon Nov 20 2000 - 12:50:33 PST


I hadn't read through the whole thing yet, but PCI is not exactly unterminated.
It uses whimpy drivers with high output Z, which serves as a series termination,
so when your voltage doubles at the end due to open load, the signal becomes
normal height, without much over/under-shooting.

Mike Mayer wrote:

> [PCI problems simulation vs. real board]
>
> PCI is meant to be unterminated and so there can be overshoot and
> ringing. That said, I can think of several things that can cause
> differences between simulated and measured results:
>
> - models (of course)
> - only looking at typ simulation data (real board may be closer to
> min or max)
> - limited bandwidth of scope used to measure board or poor
> connection to board.
>
> --
> =============================================================================
> Mike Mayer
> mwmayer@tds.net
>
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