USB – Why Thunderbolt 3 on Copper Wire is Faster Than USB 3.1


As I understand it, Thunderbolt 3 and USB 3.1 use the exact same USB-C connectors. I am aware that Thunderbolt 3 is approximately quadruple the speed of USB 3.1. I had assumed that it was because TB ran on optical fiber, but apparently this is not true, according to I also know it's not a parallel interface.

In that case, why is TB3 faster than USB 3.1? Is it something to do with the controller, or the cable itself?

Best Answer

TB is faster because it uses TWO pairs of Rx/Tx lanes, while USB 3.0/3.1 uses only one pair. USB 3.1 cables contain only one set of differential Rx/Tx pairs, while TB uses two pairs, and therefore is thicker and more expensive.

In Type-C connector, USB 3.1 uses only one set of Rx/Tx contacts, or another set, depending on which way a cable is plugged in. And a USB 3.1 host uses data multiplexer to switch to corresponding pin set. The TB uses BOTH sets of high-speed data pairs.

For the same (comparable generation) transceiver technology, 5Gb, 10Gb, whatever, the TB will be always ~2X faster, since its data path is 2x wider.

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