I still think the jitter numbers (which are in UI) should not be increasing with modulation level. (Maybe even go the other way keeping them the same in ps), but at least leave them the same (in UI as 802.3dj).
I have this for inputs so far. pam enob SNR_Tx Deterministic Jitter R_LM Random Jitter Rx FFE pre taps Px FFE post taps Rx FFE total taps Rx ffe floating tap groups Taps per Group Last floating
tap relative to the cursor A_dd Sigma_r 4 5 31. 5
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I have this for inputs so far.
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pam
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enob
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SNR_Tx
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Deterministic Jitter
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R_LM
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Random Jitter
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Rx FFE pre taps
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Px FFE post taps
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Rx FFE total taps
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Rx ffe floating tap groups
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Taps per Group
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Last floating tap relative to the cursor
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A_dd
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Sigma_r
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|
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4
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5
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31.5
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0.02
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0.95
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0.01
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8
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22
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30
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2
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6
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160
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6
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5.5
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32.5
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0.022
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0.97
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0.011
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7
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28
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35
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2
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5
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120
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8
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6
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33.5
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0.023
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0.98
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0.012
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6
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14
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20
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2
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4
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100
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Would this be reasonable start point for channel analysis?
[AMD Official Use Only - AMD Internal Distribution Only]
Good to know. I’m certainly not a n expert here either
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For KR4 (NRZ) we used Nb= 14
For KP4 (PAM4) we used Nb= 16
I can’t remember why though.
Which is the opposite direction of what you were suggesting below.
Hello Rich,
ADC ENOB is defend as = (SNDR - 1.76 dB)/6.02, furthermore SNDR and ENOB are frequency dependent. PAM4 with higher frequency will have lower ENOB, my suggestion is the following for ENOB:
PAM4 = 5.0 bits
PAM6 = 5.5 bits
PAM8 = 6.0 bits.
Please also see https://ieeexplore.ieee.org/document/8310332/figures#figures
Proposed RX FFE fixed taps:
PAM4 = 30 UI
PAM6 = 25 UI
PAM8 = 20 UI
In DJ we doubled the number of taps, here is my suggestion for last floating taps:
PAM4 = 160 UI
PAM6=130 UI
PAM8 = 100 UI
Thanks,
Ali Ghiasi
Ghiasi Quantum LLC
On Jun 26, 2025, at 2:48 PM, Richard Mellitz <richard.mellitz@xxxxxxxxx> wrote:
Hi All,
I put together a stake in the ground for 400 Gb/s COM so we can better analyze channels.
This not a recommendation. It’s starting point for consensus discussion. I’m not convinced the progression direction is correct for some the parameter makes sense. I can argue either way.
Comments and suggestions welcome.
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pam
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enob
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SNR_Tx
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Deterministic Jitter
A_dd
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R_LM
|
Random Jitter
Sigma_r
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Rx FFE pre taps
|
Px FFE post taps
|
Rx ffe floating tap groups
|
Taps per Group
|
Last floating tap relative to the cursor
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4
|
6.5
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33.5
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0.02
|
0.95
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0.01
|
8
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15
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2
|
6
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100
|
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6
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6
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31.5
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0.022
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0.93
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0.011
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7
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12
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2
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5
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65
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8
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5.5
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29.5
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0.023
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0.9
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0.012
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6
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10
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2
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4
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50
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Rich Mellitz, Samtec
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