The weird part is that it came with this extra little metal plate and some screws... And I was sitting here for a few minutes trying to sus out what in the world this was for.

Cover for the bottom? Spacer? What the heck?

Wouldn't be the first time an ebay purchase comes with bonus random hardware that has nothing to do with the product, but right before I was going to chuck it the fact that two of the holes were threaded stuck out to me.

Then I finally turned it the right way and realized it's the most amazing mPCIe accessory I've ever seen.

It's an extension plate! There's two different lengths of mPCIe cards, and some sockets won't have mounting posts for both lengths, so this lets you turn this into a 51mm full size mPCIe card if you need to use it somewhere that doesn't support half size cards! 🤓

So unfortunately, it looks like there isn't enough clearance in the T620 case for this card's SATA connector and even a right angle connector.

@warthog9 tried to talk me into replacing the connector on the board with a right angle connector, but I like the idea of just soldering a pigtail onto the mPCIe card, because SATA is literally just two pieces of twinax for transmit and receive!

@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”? 🤔

@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. https://pinouts.ru/Slots/pci_express_pinout.shtml