How’s this for a compromise?
Define a 4 lane PHY for operation over backplanes with a insertion loss of <= 35 dB at 12.9 GHz with printed circuit board routed lengths which may reach 1 meter.
Define a 4 lane PHY for operation over backplanes with a insertion loss of <= 33 dB at 7.0 GHz with printed circuit board routed lengths which may reach 1 meter.
From: Mike Dudek [mailto:mike.dudek@xxxxxxxxxx]
Sent: Tuesday, February 14, 2012 4:23 PM
To: STDS-802-3-100GCU@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_100GCU] Objective changes for the Back Plane Initiative
I think the channels defined by IEEE std.802.3ap with lengths up to at least 1m is too restrictive. To me that would imply all backplanes allowed by ap. (ie no opportunity to tighten ILD etc.)
Mike Dudek
QLogic Corporation
Senior Manager Signal Integrity
26650 Aliso Viejo Parkway
Aliso Viejo CA 92656
949 389 6269 - office.
Mike.Dudek@xxxxxxxxxx
Joel,
I understand where you’re coming from on the insertion loss. That sounds like an objective with a specification built in.
How about the following:
1) Define a 4 lane PHY for operation up to 12.9 GHz over backplane channels defined by the IEEE P802.3bj Task Force with lengths up to at least 1m.
2) Define a 4 lane PHY for operation over backplanes channels defined by IEEE Std. 802.3ap with lengths up to at least 1m.
My hope is that #1 represents the new backplane channels that can be defined by the task force and supports the NRZ position while #2 represents supporting existing channels being developed for 10GBASE-KR and 40GBASE-KR4. By removing insertion loss from #1, the task force is also permitted to have some wiggle room relative to what the final loss number needs to be.
One note is that the word “defined” in both #1 and #2 may be too literal for some. In such a case “referenced” may be the better word.
Thanks,
Brad
Hi Dave
My goal was to make sure loss and reach are defined. I added the material because we want to make sure we are talking about an fr-4 rated kind of design ... Not define a specific set of materials. Rather, make sure we are not trying to do this on the lowest fr-4 out there ... Hence improved fr-4
Take care
Joel
On 2/14/12 11:57 AM, "Chalupsky, David" <david.chalupsky@xxxxxxxxx> wrote:
Hi Joel,
Is there a way to differentiate the wording regarding materials for the two objectives? I think your intent is that “improved FR-4” has a different definition for each objective, but with the same terminology on materials it is not clear why the two objectives are distinct.
I am in favor of two objectives, just anticipating that a good deal of word-smithing will ensue.
Would a compromise be to keep the loss and reach, but drop the material?
Thx,
Dave
From: Joel Goergen [mailto:jgoergen@xxxxxxxxx]
Sent: Tuesday, February 14, 2012 11:12 AM
To: STDS-802-3-100GCU@xxxxxxxxxxxxxxxxx
Subject: [802.3_100GCU] Objective changes for the Back Plane Initiative
All
There have been some discussions around changing the following objective:
Define a 4-lane 100 Gb/s backplane PHY for operation over links consistent with copper traces on “improved FR-4” (as defined by IEEE P802.3ap or better materials to be defined by the Task Force) with lengths up to at least 1m.
To something like:
•Define a 4 lane PHY for operation over backplanes with a insertion loss of <= 35 dB at 12.9 GHz
•Define a 4 lane PHY for operation over backplanes with a insertion loss of <= 33 dB at 7.0 GHz
I don’t support this because it leaves to much variation, along with additional specifications, in the definition of the transmitter and receiver. Systems implementation of this type of specification will see 1) an increased design cost attributed to tools, modeling, and re-spins, 2) incomplete and inconsistent models providing false positives to a successful implementation, and 3) a complex set of additional metrics that will make the finished standard too complicated to follow.
The following is a much better set of objectives that allow systems vendors a path forward using current design processes and implementations.
1) Define a 4 lane PHY for operation over backplanes with a insertion loss of <= 35 dB at 12.9 GHz over links consistent with copper traces on “improved FR-4” (as defined by IEEE P802.3ap or better materials to be defined by the Task Force) with lengths up to at least 1m.
2) Define a 4 lane PHY for operation over backplanes with a insertion loss of <= 33 dB at 7.0 GHz over links consistent with copper traces on “improved FR-4” (as defined by IEEE P802.3ap or better materials to be defined by the Task Force) with lengths up to at least 1m.
I heard reference that by defining loss, material, and length, we can not meet that. I disagree. I think we are defining a loss up to 1m on improved fr-4. If it makes people feel better, the following is also acceptable from a system designers point of view”
1) Define a 4 lane PHY for operation over backplanes with a insertion loss of <= 35 dB at 12.9 GHz over links consistent with copper traces on “improved FR-4” (materials definition to be defined by the Task Force) with lengths up to at least 1m.
2) Define a 4 lane PHY for operation over backplanes with a insertion loss of <= 33 dB at 7.0 GHz over links consistent with copper traces on “improved FR-4” ( materials definition to be defined by the Task Force) with lengths up to at least 1m.
I do not support a loss only model. It is not economically feasible.
Take care
Joel Goergen