23 octobre 2026
USB 3.2 Gen 1 vs Gen 2 vs Gen 2×2 : lire les niveaux de vitesse sur une fiche technique de stockage
Le système de dénomination de l’USB-IF renomme le même matériel à chaque génération. Ce guide relie chaque désignation actuelle à son débit réel, montre où une fiche technique peut tromper, et explique quel niveau une clé USB, une carte ou un SSD portable nécessite réellement.
Cet article est disponible en anglais.
Every storage buyer eventually meets the same wall: three products, three different interface labels, no obvious way to compare them. The confusion is deliberate on nobody’s part — the USB Implementers Forum renamed the same generations more than once, so a 2015 product and a 2024 product can carry different names for identical bandwidth. This guide maps the labels to the rates that actually matter when you are specifying a programme.
The naming history, compressed
The original names were simple: USB 2.0 (480 Mb/s), then USB 3.2 Gen 1 (5 Gb/s, formerly USB 3.0), USB 3.2 Gen 2 (10 Gb/s, formerly USB 3.1), and USB 3.2 Gen 2×2 (20 Gb/s). The 2019 renaming folded all of them under the USB 3.2 umbrella, which is why a current spec sheet may say USB 3.2 Gen 1 where a 2016 one said USB 3.0 — same hardware, new label. USB4 later added its own tiering (20 and 40 Gb/s) on top.
What each tier delivers in practice
| Label | Signalling rate | Realistic throughput | Typical use |
|---|---|---|---|
| USB 2.0 | 480 Mb/s | about 35–40 MB/s | Bulk documents, giveaways, low-cost promotion |
| USB 3.2 Gen 1 (ex 3.0) | 5 Gb/s | about 400–450 MB/s | Standard flash drives, card readers |
| USB 3.2 Gen 2 (ex 3.1) | 10 Gb/s | about 900–1,000 MB/s | Fast flash drives, portable SSDs |
| USB 3.2 Gen 2×2 | 20 Gb/s | about 1,800–2,000 MB/s | High-speed portable SSDs, dual-lane devices |
Throughput is always below the signalling rate: protocol overhead, the controller, and the flash itself all take a share. A drive labelled 10 Gb/s that writes at 300 MB/s is not defective — it is limited by its controller or its NAND, not by its port.
Where a spec sheet misleads
- Read speed quoted without write speed. Sequential read is the flattering number; sustained write is where controllers show their class. Ask for both.
- Speeds quoted “up to” a rate the port cannot reach. A Gen 2 drive in a Gen 1 port runs at Gen 1 speed — the port, not the drive, sets the ceiling.
- USB-C mentioned without the protocol. USB-C is a connector shape; the protocol inside can still be USB 2.0. Check the protocol label, not the plug.
- Cable capability ignored. Gen 2×2 needs a certified dual-lane cable; an older cable caps the link at Gen 2 speed regardless of the devices at both ends.
Which tier does each product line need
| Product | Sensible tier | Why |
|---|---|---|
| USB flash drive | USB 3.2 Gen 1 for general use; Gen 2 for premium lines | Flash read/write at Gen 1 already saturates most use cases; Gen 2 matters for large file transfers |
| Memory card | Interface class on the card (e.g. UHS-I / UHS-II, SD 2.0) plus the reader tier | The slower of card and reader wins; pair them deliberately |
| Portable SSD | USB 3.2 Gen 2 or Gen 2×2 | The whole point of an external SSD is bandwidth; 10 Gb/s is the credible minimum |
| USB hub / dock | Gen 1 upstream for data; Gen 2 where video or storage expansion is offered | Bandwidth is shared across downstream ports — check the split, not just the headline rate |
How to write it into a specification
Specify the tier by its signalling rate as well as its marketing name, and state the test conditions for the quoted speed: file sizes, controller behaviour over sustained writes, and the host system used. A supplier who can reproduce the number under stated conditions is quoting a measurement; one who cannot is quoting a label.
Then test the ceiling yourself: a large sequential copy to the device, on the port you will actually ship to, on a fresh unit. If the result is within the quoted band, the specification and the product agree — which is the only outcome that protects a programme six months later.
Cet article est également publié sur le blog lingctech.com.Voir l’article original
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