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Note that where it says:

> A mini PCI Express 4G LTE modem. I used a Quectel EC25-A, but there are some from Sierra Wireless I've heard recommended too.

This is actually just a mini-pci-e adapter board that exposes the USB pins to the USB type A connector seen in the photo. It's not an actual pci-e bus device LTE modem. As shown in the example, it appears to the kernel as a USB device.

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I was racking my brain trying to figure out how they did PCI over USB 2 and then just had the modem show up as a USB device. Maybe USB-C would have made some sense, sorta. Had no idea that the mini-pci-e connector could also just be used for USB.

Most PCI cellular modems are actually USB devices, or at least can be put into USB mode.

This is something I haven't even researched yet, but are 5G modems (the ones that seem to be more M.2 slot style) also using USB, or are they finally running over the PCIe bus?

Some have a PCIe mode, but as of now you are stuck with crappy vendor drivers (if any). Default is USB. Lenovo had an issue with their crappy notebooks in this regard. Whitelist triggered if you used it in USB mode.

USB 3.2 Gen 2 Supports “up to” 10GBs, same as 5G.

Seems like there would be no reason to upgrade to PCIe, since (I assume) it would be a pretty expensive update for no meaningful change in theoretical max speed.

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