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Re: [BP] Project Objectives

Brian,
 
I am really worried that there is much more being read into the project requirements here than  the TF agreed upon.  Comments on your points are as follows:
 
1a) There has been no date stamp on any BPs associated with this TF.  Pre-existing BPs using 'improved FR-4' and meeting the channel mode are welcome.
1b) At no point was it decided that these were explicitly to be dielectriic loss-limited channels.  Low-loss channels ave stubs, so they cannot be ignored.
1c) At no point did the TF agree that existing BPs which happened to be running XAUI traffic were exempted from the TF consideration.
3) The task was to define a channel, over which the systems industry actually wants to run 10Gb serial data.  For some reason, signalling and channel capacity is brought up implicitly before these channel discussions can actually close, however.  Graphs were shown of ATCA channels at the last meeting (a form factor which the industry does value), and this seems to cause problems for one of the "available, low power solutions". If the task is, as you indicate, unilateral, then let us consider the ATCA channels and their value before assuming that this somehow violates a silicon design requirements.
 
.../Mike
From: owner-stds-802-3-blade@listserv.ieee.org [mailto:owner-stds-802-3-blade@listserv.ieee.org] On Behalf Of Brian Seemann
Sent: Friday, October 08, 2004 5:32 PM
To: STDS-802-3-BLADE@listserv.ieee.org
Subject: [BP] Project Objectives

The important initial step in our process was to set the project objectives.  These objectives and criteria framed a very viable and valuable project, and were carefully considered and ratified by the larger 802.3 body.  Early Task Force work and consensus solidified the direction we are taking.
  1. The project objectives specify operation over Improved FR-4.  This objective establishes some very key guidelines:
      a) First, it means that the project is dealing with newly designed backplanes, as there is no prevalence of Improved FR-4 in legacy backplanes.
      b) Further, the group focused very intently on defining the Dk and Df of Improved FR-4 due to the wide understanding that the material properties would be the prime determinant of channel capacity.  This means that layout discontinuities were not going to be made the prime determinant of channel capacity.
      c) Finally, the PHYs for 1G and 4-lane 10Gbps are specifically designated in the Objectives as running over the Improved FR-4 channel.  So accommodation of pre-existing channels that ran other 1G and 4-lane 10Gbps PHYs is out of this project's scope.
  2. The directive we were given was to look at the channel model as a bilateral Contract between backplane and signaling.  It was directed that the signaling must perform to at least under the line, and the backplanes must perform to at least above the line.  (In this email, I will not deal with the over-simplicity of our present model approach)  The bilateral nature of the contract means that if signaling is asked to provide margin to the contractual infractions of the backplane, the backplane will be asked to provide margin to the contractual infractions of the signaling.  The net effect is mutually-contributed, balanced margin.
  3. The directive given to the 802.3ap members was to unilaterally define the channel prior to any signaling considerations.  The rationale was that this provided a more deterministic, linear progression through the project, which is admirable.  The direction was that in the subsequent signaling evaluations, we could expect that any problems that such channel presented to the signaling could be dealt with by easing up on the channel at that later time.
  4. The Channel Ad Hoc directive was to find the worst, reasonable channel and solidify the contractual line.  And now, initial signaling evaluations have been performed on the channel.  In what I believe surprised a number of people, the results show that the channel model does not require relief.  All the signaling proved able to hit the target, even the most simple, available and low power.  Instead of being ecstatic for the industry, it seemed this frustrated a number of people.
  5. It would seem that the Task Force has done quite well in meeting objectives.  Since we have been successful in meeting objectives, and our timeline says that signaling decisions are the next item, it is appropriate to be focusing on requirements consistent with our objectives.
BrianS