Bluefield-3 B3240 | External power supply via the ATX cable

Infrastructure & Networking BlueField
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The BlueField-3 documentation states that the B3240 requires an external power connection via an 8-pin ATX cable. We initially overlooked this (our mistake) but the card still appeared functional, we were able to SSH into it and modify interface settings without issue. Later, after reseating the card, we realized the power cable was missing. I reached out to our hardware team for assistance in obtaining and connecting an appropriate 8-pin ATX cable. According to the documentation, the connector should provide a 12V power supply, but when our team measured the voltages on the board connector, they observed the following readings (values shown in red).

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Our concern is that connecting the power cable might, in the worst case, risk damaging the card or other components. Is this something we should be worried about or are we good to make that connection?

Really appreciate the help.

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Hi. Our configuration is a little bit more complex (using an HPE Server). But what I can confirm, using an PCIe 8 Pin ATX Power cable does work (that you normally connect your PCIe graphic card), works.

This:

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Hi Christian, thank you for the help and the picture. So would you say that the mismatch of voltages is nothing to be worried about?

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I`m not sure (maybe some NVIDIA employee will confirm) but IMHO this has to to with how the DPU is electrically connected. Maybe through diodes etc. the voltage you measured dropped. As this is a Input and no Output this would make sense.

It works without connecting the external cable, but then it uses power from the PCIe slot. As this is not sufficient, you have to connect the external cable.

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  1. pin1-4 is reversed. should see from another direction.
  2. there are two types of 8pin ATX power. One for GPU and one for CPU. We use more commonly seen GPU typed 8pin ATX power cord.
  3. we implement auto power capping feature. If 12v ATX does not connected board will enter force low power mode with reduced functionality. This behavior is altered in latest release, that BIOS will enforce ATX power connected otherwise will not boot.
  4. onboard power circuits will auto switch over to 12v atx if available, so there is sense/comparator facing 12v_atx. When you measure the voltage you will see non GND values, expected.
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