He thor module is connected to a 25G optical module

Robotics & Edge Computing Jetson Systems Jetson Thor
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Hello, engineers from NVIDIA.

Our company currently has a project for edge computing servers using THOR. Based on the THOR development DEMO, we are designing the schematic diagram. Our project requires a 25 optical module SFP28, but the THOR development module uses a QSFP,100G optical module. We need to change it to a 25G optical module. Currently, the sideband signals used by the 100G optical module are defined differently from those of the 25G optical module. What I want to ask is whether the 25G sideband signals can use the few signals of the 100G optical module, but it should be necessary to modify the software to control how many sideband signals to find.

The second question is that the 100G optical module uses UPHY1_TX/RX 4 5 6 7 LANE. Our 25G optical module uses one of the lanes, which is UPHY1_TX/RX 4. May I ask if this is the correct connection method.

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Please refer to the Thor design guide.

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4x 25GbE is supported. Each UPHY lane is up to 25GbE. If running at 25GbE, all 4 lanes needs to be at 25GbE with QSFP28. If using at 10GbE , then each UPHY lane could be at 10GbE, 5GbE or 2.5GbE.

SFP28 should be possible if using just 1x 25GbE lane. How many 25GbE links do you need?

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Our requirement is to use a 25G optical module with one LANE channel, namely UPHY1_TX4/RX4, and not to use the channels of the other three MGBE 100G modules. The first question is whether it is feasible to connect a LANE using a 25G optical module. The second issue is that the 100G optical module has three sideband signals: QSFP_RESET_N,QSFP_LPMODE, and QSFP_INT_N, while the 25G optical module has three sideband signals: SFP_LOS,RATE_SEL,SFP_TXDISABLE, and SFP_FAULT. Can the IO ports for these four signal inputs use the sideband signal IO ports of the 100G optical module? Moreover, the software driver needs to be modified to support the 25G optical module.

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Let’s simplify the problem. Our project needs to use a 25G optical module of SFP28. Could you please tell us how this optical module should be connected to Thor in terms of hardware

Thor module for multi 25G connector application
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QSFP28 is supported. You will need to customize the SW drivers to use SFP28. Sideband signals needs to be updated in the SW driver or you could use any other unused GPIOs.

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OK, thank you. By the way, should the UPHY0_RX4/TX4 LANE be used to connect to SFP28?

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You may need QSFP28 to SFP28 adapter or breakout cables if using Jetson Thor devkit. https://www.youtube.com/watch?v=48qv-GhjKrA&t=53s

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I just got last parts and set it up today. I got one of these on ebay “Mellanox MAM1Q00A-QSA28 QSFP28 to SFP28 100GbE to 25GbE Dynamix QSA Adapter”

I got two of these, one for Thor, one for my 10gb switch. NVIDIA/Mellanox MMA2P00-AS Compatible 10/25GBASE-SR SFP28

And a QNAP QSW-2104-2S-A-US: 2.5GbE RJ45 & 10G SFP+ switch.

I get 10gb connectivity. If I had a 25gb switch I’d guess that would be my speed with these optics.

sudo ethtool mgbe0_0

Settings for mgbe0_0:
        Supported ports: [ TP    MII ]
        Supported link modes:   Not reported
        Supported pause frame use: Symmetric Receive-only
        Supports auto-negotiation: Yes
        Supported FEC modes: Not reported
        Advertised link modes:  Not reported
        Advertised pause frame use: No
        Advertised auto-negotiation: Yes
        Advertised FEC modes: Not reported
        Speed: 10000Mb/s
        Duplex: Full
        Auto-negotiation: on
        Port: MII
        PHYAD: 0
        Transceiver: external
        Supports Wake-on: d
        Wake-on: d
        Current message level: 0x00000000 (0)

        Link detected: yes
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