Brad,
I cringe at that terminology. I was
trying to ascertain from the group which channels they thought were the problem
- loss induced channels, channels with deep nulls, or channel with
ripple. In the Signaling Ad Hoc it was discussed and requested that we
look at channels with more loss than the channel model to ascertain margin,
look at channels with deep nulls, and look at channels with ripple. It is
not just a matter of distance, but a combination of all of these effects. The
channel with the null that I provided is not even as bad as it can be, since
the backplanes used implement the QuadRoute technique, and hence the backplane
is only 0.125" thick, which helps to reduce the null effect. Furthermore,
it is only a 22" system length, and is actually above the proposed model
by approximately 5dB or more out to 6 GHz.
Loss in the right places can actually be
beneficial. It helps to reduce crosstalk and return loss. There is
an informative model limit, however, the signaling ad hoc said they wanted to
look beyond it. IBM and LSI showed they could still do it, but the penalty
looked to me potentially more taps, i.e. more power. Case #1 in general
is above the model with two minor excursions due to ripple. The skin
effect losses with 6 mil on daughtercards and 4.75mil for 20" on
backplane forces a slope that makes the ripple go below the model. Joel's
system is based on all 6 mil wide traces on daughtercard and backplane, and
this will impact the slope of the loss curve in a positive manner. .
The last channel (test case #7) has ripple
in it that is due to some stub and adjacent slot spacing. You will see it
doesn't exceed the proposed model until 12 GHz @ -55 dB. I have a
hard time believing that the exceeding of the model was the problem, but rather
the overall ripple in the channel, which Mary
Mandich pointed out could be a
problem for some equalization techniques, which I have also seen.
So I am trying to find out from the people
who didn't want these channels included which ones they were specifically
opposed to. As people have said, it will help us to understand where
things will break.
John
-----Original Message-----
From: owner-stds-802-3-blade@LISTSERV.IEEE.ORG
[mailto:owner-stds-802-3-blade@LISTSERV.IEEE.ORG]
On Behalf Of Booth,
Bradley
Sent: Tuesday, October 05, 2004
6:19 PM
To:
STDS-802-3-BLADE@LISTSERV.IEEE.ORG
Subject: Re: [BP] Question
regarding Channels
John,
I've been sitting on the
fence watching this, and I wonder if this is more about whether or not to
support legacy vs. greenfield channels. If that is the case, the answer
may be harder to achieve, but there may be some room for a compromise.
Something that came to mind recently is that this could be similar to the
existing Cat 6 and augmented Cat 6 discussion going on in 10GBASE-T. The
interesting thing is that the model of a 55m channel of Cat 6 (legacy) is very
similar to a 100m channel of augmented Cat 6 (greenfield). If there is a
desire to support legacy backplanes (primarily ATCA which would support the
Broad Market Potential requirement), but the reach on those backplanes is less
than the 1m target objective, then is it possible that the legacy channel model
(for its specified reach) could be equivalent to greenfield channel model
at the 1m reach?
In other words, if the
ATCA max. reach is 32", then could the channel models for that reach be
equivalent to a greenfield channel that is achieving ~40"? So, if
you specify the channel model based on the existing ATCA channel at 32",
vendors should be able to use better materials to achieve the required 1m
reach. This would permit support for legacy ATCA platforms while
permitting better materials to be used for greater reaches.
Thoughts? Or should
I just go back to sitting on the fence?
Thanks,
Brad
From:
owner-stds-802-3-blade@listserv.ieee.org
[mailto:owner-stds-802-3-blade@listserv.ieee.org] On Behalf Of DAmbrosia, John F
Sent: Tuesday, October 05, 2004
1:46 PM
To: STDS-802-3-BLADE@listserv.ieee.org
Subject: Re: [BP] Question
regarding Channels
All,
The reflector appears to
be very quiet. I would really like to have this discussion so we can try
to move forward.
John
-----Original Message-----
From:
owner-stds-802-3-blade@listserv.ieee.org
[mailto:owner-stds-802-3-blade@listserv.ieee.org] On Behalf Of DAmbrosia, John F
Sent: Tuesday, October 05, 2004
10:39 AM
To:
STDS-802-3-BLADE@listserv.ieee.org
Subject: [BP] Question regarding
Channels
All,
Since time did not allow the conversation last week,
I
would
like to talk further on the reflector to understand the opposition to the
different
channels
that were proposed.
I will point to my test cases as a starting point,
but the conversation really applies to all of the channels.
As I see it, we have the
following types of impairments in the total
system-
1. Loss
dominated
2.
Significant
stub effects that cause deep nulls
3.
Ripple
in the
channel
4.
NEXT
5.
FEXT
6.
Return
Loss
I believe most of the opposition arose from
1,
2,
3 and
6, but would like to have this conversation now.
The comments that I heard
regarding my channels were the following -
·
The
data is not freely available. - This is no longer true,
as I indicated last week.
·
The
data violates the informative channel model. I believe there
were different cases where this happened.
o
Case 1
had minor ripple below the mask.
o
Cases
2 and 3 were margin cases that the Signaling Ad Hoc had requested.
o
Case 6
came from a 22" link with top layer backplane connections. This
channel was justified for its potential appearance in systems where
all
cost
was being minimized, so counterboring was not assumed.
o
Case 7
had a resonance ripple at approximately -55dB at 11 GHz.
Once
again this was a test case asked for by the Signal Ad Hoc to examine channel
ripple. Otherwise up to 11 Ghz it is 5 to 15 dB above the
informative mask
·
Return
loss is too high. In my opinion, this is a
contradictory statement. The mask that I proposed that fit my
data was not as aggressive as Joel's channels (#1,2,3,6,7,8,14,17,18).
All of
these models violated the proposed SDD11
mask
in the
lower frequency region, which I proposed.
·
The
data hadn't been seen. This is a partially true statement.
Tyco
has been diligent in presenting the data as quickly as gathered and
processed. The SDD21 channel data for Cases 2, 4,5,6, and 7
was
posted to the Signaling Ad Hoc reflector for the
Sept 9 meeting.
So I reviewed Joel's data that was
proposed
Case #1 - 4_3_4 (4000-13) Total
11"
Case #2 - 7_3_7 (4000-13)
Total 17" has xtalk
Case #3 - 10_3_10 (4000-13)
Total 23"
Case #6 - 4_10_4 (4000-13)
Total 18"
Case #7 - 7_10_7 (4000-13)
Total 24" has xtalk
Case #8 - 10_10_10 (4000-13)
Total 30"
Case #14 - 3_3_15_7 (4000-13)
Total 29"
Case #17 - 7_20_7 (4000-13) Total 34"
has xtalk
Case #18 - 10_20_10 (4000-13)
Total 40"
All of these test channels are well above the channel
model. We will still need a test case that falls very closely
on the
informative
channel
model, which is where the Tyco channels 1 - 3 are falling
(with included margin cases). From both IBM and
LSI's analysis these channels were solvable.
The
StatEye analysis results were much more pessimistic (which is an
on-going problem with StatEye that is being
investigated) than the analysis of these companies and the
crosstalk was not applied properly.
So to me it looks like overall loss
isn't necessarily the big problem. Loss can be very advantageous,
as was demonstrated at last week's meetings, as to how it can actually help
reduce xtalk and return loss. Ripple and nulls on the other hand appear
to be the bigger problem.
So I would like to open
up discussion as to which Tyco channels people were most concerned about.
Also, I do not know what to propose for a "weighting"
scheme, so any suggestions on this would be of extreme use in helping us to
reach consensus and move forward.
Cheers!
John D'Ambrosia
Manager, Semiconductor Relations
Global CC&CE
Tel 717.986.5692
Fax 717.592.2470
Cell 717.979.9679