USB was supposed to make life simpler: one port for everything. Today it has become one of the most confusing topics in consumer computing, with names changed several times, identical ports with different capabilities and cables that look the same but aren't. The way out is to separate two concepts that almost everyone mixes up: the shape of the connector and the protocol that runs through it.
Connector and protocol are two different things
The connector is the physical part: USB-A, the classic rectangle; USB-B, the square one on printers; Micro-USB, on older phones; USB-C, small, oval and reversible. The protocol is the "language" devices use to exchange data: USB 2.0, USB 3.2, USB4, Thunderbolt.
The key point: a USB-C port says nothing about speed. It may be USB 2.0 at 480 megabits per second, or a USB4 or Thunderbolt port at 40 gigabits. The same goes for cables.
Versions and speeds
| Technical name | Recent marketing name | Maximum speed |
|---|---|---|
| USB 2.0 | — | 480 Mbit/s |
| USB 3.2 Gen 1 (formerly USB 3.0) | USB 5Gbps | 5 Gbit/s |
| USB 3.2 Gen 2 | USB 10Gbps | 10 Gbit/s |
| USB 3.2 Gen 2x2 | USB 20Gbps | 20 Gbit/s, USB-C only |
| USB4 | USB 40Gbps | up to 40 Gbit/s |
| USB4 version 2.0 | USB 80Gbps | up to 80 Gbit/s |
The same speed has been named differently over the years: USB 3.0, then USB 3.1 Gen 1, then USB 3.2 Gen 1. That's why the clearest datasheets state the speed in gigabits directly, and that's the figure to look for.
Speeds are theoretical. An external drive slows down because of its internal limits, the adapter in the enclosure or the cable. An NVMe SSD in a 10 Gbit/s enclosure won't reach the speed it would have inside the PC, but it will still be much faster than a hard disk.
Thunderbolt
Thunderbolt is a technology created by Intel and Apple which, since version 3, uses the USB-C connector. Thunderbolt 3 and 4 reach 40 Gbit/s; Thunderbolt 5 doubles the bandwidth. USB4 is largely based on the Thunderbolt 3 specification, and devices are broadly compatible with each other.
What Thunderbolt adds in practice:
- guaranteed minimum requirements: for example, Thunderbolt 4 requires support for at least two external monitors and for charging;
- transport of PCI Express, which enables complex docks, capture cards and enclosures for external graphics cards;
- daisy-chaining several devices.
Thunderbolt ports are recognised by the lightning bolt symbol next to the connector; without the symbol, check the computer's specifications.
The cable matters
Many problems come from the cable, not the port. A cheap USB-C cable, the kind supplied for charging, often carries only USB 2.0 data. Connected to a fast external SSD, it makes it run at a fraction of its speed, without any error message.
To choose:
- for fast data you need cables rated at 10, 20, 40 or 80 Gbit/s; certified cables often show the speed on the connector or the packaging;
- passive high-speed cables are necessarily short; beyond a certain length you need active cables, which cost more;
- for USB-C monitors, the cable must support video as well as data;
- for high-power charging you need a cable with a suitable identification chip.
A simple trick: keep fast cables separate from charging ones, perhaps with a label. It saves a lot of troubleshooting.
Common problems and how to fix them
- Slow external drive: check that port, cable and enclosure support the same speed. USB 3 ports on USB-A often have a blue internal tab or an SS (SuperSpeed) mark next to them.
- The device disconnects by itself: it may be insufficient power; try a rear port on the PC or a powered hub. On Windows, also check USB selective suspend in the power options.
- USB-C monitor that won't turn on: the computer's port might not support video output. Look for the DisplayPort or Thunderbolt symbol next to the port.
- Interference with 2.4 GHz Wi-Fi: USB 3 ports and devices can disturb nearby wireless receivers, such as those for mice and keyboards. Moving the receiver away with an extension cable often solves it.
Hubs and docks
A hub splits a port's bandwidth among several devices: four drives on a 5 Gbit/s hub share those 5 Gbit/s. A Thunderbolt or USB4 dock offers more bandwidth and more features, such as video, wired networking and charging, but costs more. In my work, for laptop workstations, a quality dock is one of the purchases that pays off most: a single cable connects everything.
In short
- USB-C is a connector, not a speed: the protocol is what counts.
- In datasheets, look for the speed in gigabits, not the version name.
- USB4 and Thunderbolt share the connector and much of the technology.
- The cable is often the bottleneck: charging cables are almost always slow.
- Hubs and docks share the bandwidth of the port they are connected to.
