Re: [802.3_100GCU] Objective changes for the Back Plane Initiative
Title: Re: [802.3_100GCU] Objective changes for the Back Plane Initiative
Scott
You can not specify a single source in a standard ... At least it isnt a good idea. We don’t specify manufacturers, we define specifications.
I can create a meg6 stack detail that will not meet the objective. I can define a meg6 stack detail that has as much loss as an fr-4 material.
I started this thread and I think it is going in an off direction. My point was that we need to specify approximate length, signal rate, and basic material floor. We could be better then that, but you would not want to include less then that as part of the solution space we specify to. The follow statements define that and meet all the concerns of what I have read or heard.
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.
We could remove the parenthesis and text within them. In doing so, we specify a rate, a length range to a maximum, and that we are using some kind of laminated resin with copper traces that are better then fr-4, which is the perceived minimum. It is my opinion that the length should be specified as a max, which it is, and the material be specified as a min, which it is.
With these as the objectives, we will be able to establish a transmitter, a reciever, and a suitable channel with which we will have specifications to design, debug, and ship the combination of the three..
Joel
On 2/14/12 4:47 PM, "Scott Kipp" <skipp@xxxxxxxxxxx> wrote:
Dave,
I agree with your point and propose that this could help us distinguish the two markets. For NRZ, there doesn’t appear to be an improved FR-4 material that meeting this requirement, but there is a Meg6 that meets the requirements of 0.89 dB/inch (35dB/39.4”) at 12.9GHz. For PAM-4, there are some FR-4 materials that meet the requirements of 0.84dB/inch (33dB/39.4”) at 7.0GHz according to Kochuparambil_01a_0112.
This shows that there is a big difference for what we are proposing for the two PHYs. While I don’t think that most NRZ implementations will be based on Meg6, the implementer can use the material of their choice and go for a shorter distance.
How about an objective like:
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 Meg6 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” with lengths up to at least 1m.
We could add in the dB/inch for each material in the channel definition.
Kind regards,
Scott
From: Chalupsky, David [mailto:david.chalupsky@xxxxxxxxx]
Sent: Tuesday, February 14, 2012 11:58 AM
To: STDS-802-3-100GCU@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_100GCU] Objective changes for the Back Plane Initiative
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