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Ewen McNeill

@kwf TIL.

There’s at least 7 contacts in the SATA connector though, which is rather more than 4. Are the rest just “yeah, we put in a lot of ground connections for signal integrity”? 🤔

5 May 2022 at 3:27 | Wall-to-wall | Open on cloudisland.nz
5 comments
Kenneth Finnegan

@ewenmcneill that's absolutely it. Three grounds to help keep the impedance of the two pairs controlled and isolated from each other.

It's extremely common on high speed connectors to weave signal pairs with grounds between them. I.e. go look up the pin out for PCIe slots. pinouts.ru/Slots/pci_express_p

5 May 2022 at 3:34 | Open on social.afront.org
Kenneth Finnegan

@ewenmcneill there's a non-standard convention that vendors like Supermicro uses to optionally inject 5V on one of the three ground pins to power SATADOMs, which are tiny SSDs that hang right off the SATA connector on the motherboard.

5 May 2022 at 3:36 | Open on social.afront.org
Attie Grande

@kwf @ewenmcneill Wait... THAT'S how they're powered?!

Does the motherboard detect a short and not inject power as appropriate, or are these dedicated DOM / non-standard connectors?

5 May 2022 at 8:34 | Open on mastodon.online
Kenneth Finnegan

@attie @ewenmcneill They must have some kind of detect logic on the motherboard, but they're fully functional normal SATA ports.

I think on SuperMicros they're conventionally the one yellow port that has power.

5 May 2022 at 16:48 | Open on social.afront.org
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