[zeusk]

> copper can barely support 10G and is terribly power hungry when it does that.

AFAIK, thunderbolt cables are also copper - so what trickery do they use for supporting USB4-80? i believe both connectors use differential pair wires for signalling.

[retatop]

It's simply length. Ethernet is expected to work on 50-100m runs, while USB4 specifies maximum cable lengths of 2m even for just 5gbps (at least for passive cables). 80gbps is 0.8m

[crote]

The longer Thunderbolt (which is actually just USB4) cables internally use fiber optics for data transmission, with converters to copper in each connector. Even the medium-distance (3 meter) ones have signal quality boosters in each connector matched to the kind of signal degradation that kind of cable will experience.

Completely passive TB4/TB5 cables max out at about 80 centimeters.

[tliltocatl]

Besides what retatop and crote said - USB4 uses either binary or PAM-3, 10GBASE-T uses PAM-16. Higher modulation means lower frequency bandwidth (so longer and/or crappier cable), but also more current-hungry line driver and more current required to keep noise manageable.