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
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
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