[ibis-macro] Comments on BIRD 156 (Redriver)

From: "Walter Katz" <wkatz@xxxxxxxxxx>
To: "IBIS-ATM" <ibis-macro@xxxxxxxxxxxxx>
Date: Tue, 7 May 2013 13:41:09 -0400 (EDT)
All,

 

SiSoft has carefully reviewed the latest draft of Redriver BIRD 156 with
the intent of incorporating Retimers. Before we spec Retimers, we believe
several issues in BIRD 156 should be resolved:

 

1.       BIRD 156 only discusses Time Domain simulation, and by
implication prohibits Statistical simulation. Although Redrivers are
typically not LTI, we have worked with Redriver models that support
statistical simulation.  BIRD 156 as currently written would effectively
remove this capability (or make it a point of contention), which would
negatively impact our customers.

 

2.       The Reference Flows in IBIS 5.1 describe how to perform
statistical and time domain simulations with all Tx/Rx combinations of
Init_Returns_Impulse  and GetWave_Exists.  The latest draft of BIRD 156 is
a good step in this direction, however we feel the flow discussion is
still incomplete.  It's not clear that leveraging the existing Flow
documentation "according to the AMI flow defined in the specification for
channels without redriver" is adequate here. The Redriver TX waveform is
inherently different than the traditional case, and we believe the
different possible Rx/Tx combinations need to be described in more detail.

 

3.       The last paragraph of the proposed BIRD states that all Jitter
and Noise in a Redriver must be inserted by the model's GetWave function.
This effectively precludes the ability to model noise by any other means.
The problem here is that Time Domain simulations provide a limited sample
size (at best), and there are noise processes in Redrivers suitable to
semi-analytic treatments. We believe this last paragraph should therefore
be dropped.

 

We are still assessing the best way to enhance the existing text to
address issues 1 and 2.  We are working to provide text for enhancing the
BIRD but will not be able to do so in time for today's meeting. That
notwithstanding, we wanted to identify our issues in advance of the
meeting so that everyone has time to think about them.

 

Walter

 

 

Walter Katz

 <mailto:wkatz@xxxxxxxxxx> wkatz@xxxxxxxxxx

Phone 303.449-2308

Mobile 303.335-6156
[ibis-macro] Comments on BIRD 156 (Redriver)

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