I can't tell if this is a trick question that has something to do with a quirk of USB running multiple lanes in parallel to get higher speeds.

Because if not then it's the same as any specification for connecting devices that allows for multiple speeds. It runs at the lowest of the max speeds supported of everything in the chain.

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riobard an hour ago | parent [-]

That's exactly the issue. I'm just pointing out that it's a fantasy to hope for simple numbering of max supported speeds will simplify the current USB mess.

It will not.

Consumers would expect plugging a 20Gbps device into a 40Gbps port should result in 20Gbps negotiated speed. In reality it will mostly likely end up at 10Gbps (or less) because of the mess.

	▲	adrian_b 35 minutes ago \| parent \| next [-]
		Older Thunderbolt devices were not compatible with USB, so plugging them into an USB Type C port would not work. Newer Thunderbolt/USB 4 devices do not have any technical reason for preventing them to work as USB 3.2 2x2, i.e. to work at 20 Gb/s when plugged into a 20 Gb/s host port, and vice-versa for 20 Gb/s devices plugged into a USB 4/Thunderbolt host port, because both Thunderbolt and 20 Gb/s USB need the same wires in the cable and connector. I do not know if all USB 4 controllers also work at 20 Gb/s (USB 3.2 2x2), but if they do not work that should be considered a bug.
	▲	28 minutes ago \| parent \| prev [-]
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