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I have two SoCs that are mounted on a the same carrier board using SODIMM connector. The two SoC are mounted very close to each other, the entire carrier board is smaller than 15x15 cm

I need to connect the two computers to each other using cross over Ethernet so they can talk back and forth. Given that I am not using any RJ45 or any sort of cables and the Ethernet pins of SoC-A is being directly connected to the Ethernet Pins of SoC-B using traces on the PCB, do I need to use any magnetics? Can I just directly connect the SODIMM pins to each other ?

Distance between the two SODIMM pins are about 1 or 2 cm

user258353
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    Does this answer your question? [Ethernet without magnetics?](https://electronics.stackexchange.com/questions/51754/ethernet-without-magnetics) – Finbarr Aug 03 '20 at 20:49
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    It kind of depends. Do they have identical PHYs? Do they have same supply voltage? Are they powered up at the same time from the same supply voltage? If so, maybe DC connection can work if the PHYs support that. If not, they can be capacitively coupled, if the PHYs support that. – Justme Aug 03 '20 at 20:50
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    Or this? [Connecting two Ethernet PHY without magnetics?](https://electronics.stackexchange.com/questions/90330/connecting-two-ethernet-phy-without-magnetics) – Finbarr Aug 03 '20 at 20:51
  • @Justme Both SoCs are identical (or i might switch to another one from the same family). Both SoCs are pin compatible with their product of families so the DC Volt and other properties should be almost identical – user258353 Aug 03 '20 at 21:08
  • @Finbarr good article. although that person is trying to connect two different board with voltage difference, but i am sure there will be similarities. I will check it out - thanks – user258353 Aug 03 '20 at 21:10
  • Yeah, this question has been asked a few times now – Voltage Spike Aug 03 '20 at 22:15
  • @user258353 did either of those answer your question? – Voltage Spike Aug 03 '20 at 22:18
  • In addition to being a many-time duplicate, this is fundamentally unanswerable without a detail knowledge of the PHYs in question (which the question fails to even identify!) While grossly out of spec, the reality is that you can in nice conditions interoperate with Ethernet gizmos using a series capacitor, which goes to show the degree to which *implementation detail* governs the ultimate answer here. – Chris Stratton Aug 04 '20 at 04:39

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