What Are USB Gen 1, Gen 2

What Are USB Gen 1, Gen 2

Finding the fastest USB connection used to be easy: choose USB 3.0 instead of 2.0. But now, you’ll need to know the difference between USB 3.2 Gen 1, Gen 2, and Gen 2×2—and what various types of “SuperSpeed” mean, too.

USB Naming Used to Be Simple

USB-C cable next to USB-C Compatible laptop
Once upon a time, USB came in two main flavors, 2.0 and 3.0. All you needed to know about them was 3.0 was faster than 2.0. You could buy a USB 2.0 flash drive and plug it into a computer that had USB 3.0 slots, and it would still work—just at the slower USB 2.0 speeds. Buying a USB 3.0 drive and plugging it into a USB 2.0 port would give you USB 2.0 speeds, too.
If you wanted the fastest speed possible, you’d get a USB 3.0 drive and plug it into a USB 3.0 USB port. It was simple and straightforward. But everything changed with USB 3.1.

USB 3.1 Muddied the Naming Waters

The USB Implementors Forums (USB-IF) maintains USB specifications and compliance, and it’s behind the naming schemes found on USB cables and devices. When it introduced USB 3.1, rather than keep things simple and let that name differentiate from USB 3.0, it called the new standard “USB 3.1 Gen 2.” USB 3.0 was retroactively renamed “USB 3.1 Gen 1.”
To further complicate things, the transfer speeds themselves received names. USB 3.1 Gen 1, originally known as USB 3.0, is capable of 5 Gbps transfer speeds—that’s called SuperSpeed.
USB 3.1 Gen 2 is capable of 10 Gbps transfer speeds—that’s called SuperSpeed+. Technically, it accomplishes this by using 128b/132b encoding in a full-duplex communications mode. Full-duplex communication is exciting because that means information can be transferred and received at the same time. That’s why it’s faster.
The difference between the two was slightly confusing. But, as long as you remembered Gen 2 was better than Gen 1, you were good to go. To help differentiate the speeds, USB-IF also implemented logos, which manufacturer can only use by passing a certification to prove a cable matches the promised specs.

USB 3.2 is Even Faster and More Confusing

Image of PDF describing USB 3.2 naming
Last September, the USB-IF detailed out new possible speeds for USB-C, and the beginnings of the USB 3.2 specification. USB 3.2 will be capable of 20 Gbps speeds. That’s double the transfer speeds of USB 3.1 Gen 2. If you’re wondering how the cables are doubling their speed so quickly without changing size or connectors, it’s straight forward. USB products capable of 20 Gbps have two 10 Gbps channels. Think of it as more wiring jammed into the same cable.
Just like in previous iterations, this new standard is backward compatible for basic usage—but you won’t get the faster speed without all new hardware. If you buy a hard drive that promises a 20 Gbps transfer rate and plug it into your current computer, the hard drive will work, but at slower speeds that the USB ports on your machine can provide. You’ll have to update both ends of the connection to enjoy all the new benefits.
At Mobile World Congress 2019, the USB-IF announced the branding and naming schemes for the new standard. And once again, the previous naming will be discarded and changed retroactively.
Going forward, what used to be USB 3.0, with 5 Gbps transfer speeds, will be USB 3.2 Gen 1. USB 3.1 Gen 2, with its 10 Gbps speeds, will be renamed to USB 3.2 Gen 2.
The new 20 Gbps standard will be named USB 3.2 Gen 2×2, breaking the predictable pattern. Physically, this has two 10 Gbps channel, so it literally is 2×2. There’s a logic to the name, but it’s confusing, and you have to understand the hardware to realize it makes any sense.

Manufacturers Should Refer to “SuperSpeed” Instead

Amazon Basics USB-C cables
USB-IF doesn’t want consumers to see these terms. Instead, it wants Gen 1 products marketed as SuperSpeed USB. It suggests manufacturers market Gen 2 products as SuperSpeed USB 10 Gbps and Gen 2×2 as SuperSpeed USB 20 Gbps. But that doesn’t mean manufacturers have to use these names. Manufacturers can use the Gen 2.2 nomenclature—or if they don’t bother to submit to testing and compliance, they can forgo the logos and use any name they feel like.
If manufacturers do comply, the naming issue is pretty straight forward. Look for “SuperSpeed” in the name and check if there’s a number. If you don’t see one, it’s the slowest USB 3.2 type. If you see a 10 or a 20, that’s the promise of 10 Gbps or 20 Gbps transfers. It might have been better if USB-IF had gone with SuperSpeed USB 5 Gbps for the slowest type. But at least it’s fairly straight forward.
In theory, USB logos should help. As seen in the image above, the SS and 10 denote that USB cable as a SuperSpeed cable capable of 10 Gbps transfers. Unfortunately, the USB-IF has not shown the official certification mark for SuperSpeed USB 20 yet. Presumably, it should be the same logo as above, just with a 20 in its place. But we don’t know that for certain yet.
If you remember USB-C’s early issues, this will probably seem very familiar. Read carefully before buying cables, and buy them from reputable, trusted sources. In the past, we’ve recommended Amazon Basics cables—but even with those you still need to look carefully. For instance, this Amazon Basics cable is USB-C but only offers 2.0 speeds. This Amazon Basics cable, which looks practically the same, offers 10 Gbps transfers and is marked as USB 3.1 Gen 2. And, of course, this doesn’t just apply to USB cables. It applies to any piece of hardware that uses USB-C.
Unfortunately, this is still a mess of confusing terms. You’ll need to do your due diligence when buying USB hardware to know exactly what you’re getting.

No comments:

Post a Comment