Re: [802.3_E4AI] [EXTERNAL] Re: [802.3_E4AI] COM starting values for 400

Thread Links	Date Links
Thread Prev	Thread Next	Thread Index	Date Prev	Date Next	Date Index

This is what I have so far.

pam	enob	SNR_Tx	Deterministic Jitter	R_LM	Random Jitter A	Rx FFE pre taps	Rx FFE post taps	Rx FFE total taps	Rx ffe floating tap groups	Taps per Group	Last floating tap relative to the cursor
pam	enob	SNR_Tx	A_dd	R_LM	Sigma_r	Rx FFE pre taps	Rx FFE post taps		Rx ffe floating tap groups	Taps per Group	Last floating tap relative to the cursor
4	5	31.5	0.02	0.95	0.01	15	30	45	2	6	150
6	5.5	32.5	0.01547	0.97	0.00774	12	24	36	2	5	120
8	6	33.5	0.01333	0.98	0.00667	10	20	30	2	4	100

Perhaps this is starting point for a Gitlab branch.

… Rich Mellitz, Samtec

From: richard.mellitz@xxxxxxxxx <richard.mellitz@xxxxxxxxx>
Sent: Monday, July 7, 2025 11:00 AM
To: 'Sridhar Ramesh' <sramesh@xxxxxxxxxxxxx>; STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx
Subject: RE: [802.3_E4AI] [EXTERNAL] Re: [802.3_E4AI] COM starting values for 400 G

Hi Sridhar,

It thought about that motivation. It seems better for interconnect. I’d like to hear others weigh in on this.

The reflector seems to be a good place formulate a starting point for all this as if seems to reach a lot of people.

… Rich Mellitz, Samtec

From: Sridhar Ramesh <sramesh@xxxxxxxxxxxxx>
Sent: Monday, July 7, 2025 12:13 AM
To: STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx; Richard Mellitz <richard.mellitz@xxxxxxxxx>
Subject: Re: [802.3_E4AI] [EXTERNAL] Re: [802.3_E4AI] COM starting values for 400 G

Hi Rich, Ali and all,

Thanks for initiating this discussion. I have a little nit to pick regarding the FFE taps.

I think they should be inversely proportional to the baud rate for a "well-behaved" channel, in addition to being monotonic for PAM4, 6 and 8. I understand that lower PAM has higher channel loss, but residual ISI targets can be more relaxed, so let's call that a wash. Also, didn't we have something like 20 taps for 200G, which has to double roughly for 400G?

Hence, I would recommend the following -

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
pam	enob	SNR_Tx	A_dd	R_LM	Sigma_r	Rx FFE pre taps	Px FFE post taps		Rx ffe floating tap groups	Taps per Group	Last floating tap relative to the cursor
4	5	31.5	0.02	0.95	0.01	15	30	45	2	6	150
6	5.5	32.5	0.022	0.97	0.011	12	24	36	2	5	120
8	6	33.5	0.023	0.98	0.012	10	20	30	2	4	100

Let me know if you have any differences of opinion.

Thanks,

Sridhar

From: Richard Mellitz <richard.mellitz@xxxxxxxxx>
Sent: Tuesday, July 1, 2025 10:33 AM
To: STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx <STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_E4AI] [EXTERNAL] Re: [802.3_E4AI] COM starting values for 400 G

This email was sent from outside of MaxLinear.

This is what I get.

>> lev= [4 6 8];

log2(4)./log2(lev)*.01

ans =

0.0100 0.0077 0.0067

Sent from my iPhone

On Jul 1, 2025, at 1:21 PM, Mike Dudek <mdudek@xxxxxxxxxxx> wrote:

Yes. Add = 0.02 UI and sigma_r = 0.01 UI for PAM 4 with values for PAM6 and PAM8 having the same ps.

From: Richard Mellitz <richard.mellitz@xxxxxxxxx>
Sent: Tuesday, July 1, 2025 10:09 AM
To: STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_E4AI] [EXTERNAL] Re: [802.3_E4AI] COM starting values for 400 G

Lock down Add = 0. 02 UI and sigma_r = 0. 01 UI for PAM 4? Get Outlook for iOS From: Upen Reddy Kareti (ureddy) <00000d999961d690-dmarc-request@ listserv. ieee. org> Sent: Tuesday, July 1, 2025 12: 16 PM To: STDS-802-3-E4AI@ LISTSERV. IEEE. ORG
ZjQcmQRYFpfptBannerStart
Prioritize security for external emails:
Confirm sender and content safety before clicking links or opening attachments
  Report Suspicious   ‌
ZjQcmQRYFpfptBannerEnd
Lock down Add = 0.02 UI and sigma_r = 0.01 UI for PAM 4?

Get Outlook for iOS
From: Upen Reddy Kareti (ureddy) <00000d999961d690-dmarc-request@xxxxxxxxxxxxxxxxx>
Sent: Tuesday, July 1, 2025 12:16 PM
To: STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx <STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_E4AI] [EXTERNAL] Re: [802.3_E4AI] COM starting values for 400 G

I support Mike Dudek’s position on Jitter ( in Ui terms) both A_dd and Rj
keep in ps terms the same
-Upen
From: Mike Dudek <mdudek@xxxxxxxxxxx>
Date: Monday, June 30, 2025 at 4:16 PM
To: STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx <STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_E4AI] [EXTERNAL] Re: [802.3_E4AI] COM starting values for 400 G
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).

From: Richard Mellitz <richard.mellitz@xxxxxxxxx>
Sent: Monday, June 30, 2025 1:26 PM
To: STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx
Subject: [EXTERNAL] Re: [802.3_E4AI] COM starting values for 400 G

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
ZjQcmQRYFpfptBannerStart
Prioritize security for external emails:
Confirm sender and content safety before clicking links or opening attachments
  Report Suspicious   ‌
ZjQcmQRYFpfptBannerEnd
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
0.02
0.95
0.01
8
22
30
2
6
160
6
5.5
32.5
0.022
0.97
0.011
7
28
35
2
5
120
8
6
33.5
0.023
0.98
0.012
6
14
20
2
4
100

Would this be reasonable start point for channel analysis?

From: Bowman, Kurtis <Kurtis.Bowman@xxxxxxx>
Sent: Thursday, June 26, 2025 9:03 PM
To: richard.mellitz@xxxxxxxxx; STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_E4AI] COM starting values for 400 G

[AMD Official Use Only - AMD Internal Distribution Only]

Good to know. I’m certainly not a n expert here either

Thanks,
Kurtis
From: Richard Mellitz <richard.mellitz@xxxxxxxxx>
Sent: Friday, June 27, 2025 8:49:34 AM
To: STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx <STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx>
Subject: Re: [802.3_E4AI] COM starting values for 400 G

Caution: This message originated from an External Source. Use proper caution when opening attachments, clicking links, or responding.

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.

From: Ali Ghiasi <aghiasi@xxxxxxxxx>
Sent: Thursday, June 26, 2025 6:31 PM
To: Richard Mellitz <richard.mellitz@xxxxxxxxx>
Cc: STDS-802-3-E4AI@xxxxxxxxxxxxxxxxx
Subject: Re: [802.3_E4AI] COM starting values for 400 G

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.

pam
enob
SNR_Tx
Deterministic Jitter
A_dd
R_LM
Random Jitter
Sigma_r
Rx FFE pre taps
Px FFE post taps
Rx ffe floating tap groups
Taps per Group
Last floating tap relative to the cursor
4
6.5
33.5
0.02
0.95
0.01
8
15
2
6
100
6
6
31.5
0.022
0.93
0.011
7
12
2
5
65
8
5.5
29.5
0.023
0.9
0.012
6
10
2
4
50

Rich Mellitz, Samtec

To unsubscribe from the STDS-802-3-E4AI list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-E4AI&A=1

To unsubscribe from the STDS-802-3-E4AI list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-E4AI&A=1
To unsubscribe from the STDS-802-3-E4AI list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-E4AI&A=1
To unsubscribe from the STDS-802-3-E4AI list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-E4AI&A=1
To unsubscribe from the STDS-802-3-E4AI list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-E4AI&A=1
To unsubscribe from the STDS-802-3-E4AI list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-E4AI&A=1

To unsubscribe from the STDS-802-3-E4AI list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=STDS-802-3-E4AI&A=1