More than ten years ago, USB bus entered the mainstream vision, provided a new storage direction, and pulled many peripherals into their own camp with a unified standard. This is their great contribution to the whole industry, and no one will deny it. However, organizations promoting USB have special naming skills, which are elusive: today, more than a decade later, three major versions of USB standards have evolved, not only creating a lot of aliases, but also the emergence of USB 3.1, GEN1 and Gen2, not to mention the interface shape definitions of mini, micro and type ABC.

Analysis and summary of USB interface standard

This makes us ordinary people see that it’s a pain. In the past, we used to judge which is faster from the color of the interface and plug. Now, looking at these new things, we can’t distinguish them clearly. People who don’t want to name usb-if and taste the back pot, it’s time to make a good general ledger.


Looking back at USB, from 1.0 20 years ago to 3.0, which is widely accepted today, the USB standard has experienced four versions of iteration: 1.0, 1.1, 2.0 and 3.0. Looking at the Arabic numerals alone, people who have passed mathematics in primary school can know which version is more advanced. However, usb-if has a hobby of using stage names. They also named the transmission rate: 1.5mbit/s is called low speed, 12mbit / S is called full speed, 480mbit / S is called hi speed, and 5Gbit / S is superspeed. The impact of language is much greater than cold numbers.

Analysis and summary of USB interface standard

Unfortunately, the transmission rate is bound to be linked to the USB standard version, so usb-if feels that it is very interesting to call several USB versions directly with the name of speed, such as hi speed USB and superspeed USB. As a result, the problem comes. When there are many names for a thing, once it is mixed, it will make people confused. Everyone looks very fast. How can I know which one is USB 3.0? Moreover, USB also has a great feature called downward compatibility, so usb-if simply allows the new standard to “eat” the old standard, and then divides the old transmission rate under the new standard. Therefore, in rare cases, you can see wonderful things like full speed USB 2.0.

Analysis and summary of USB interface standard

This mess should have been a situation that could not be cleaned up. Fortunately, usb-if thought of a surprise move at the moment of promoting USB 3.0 – changing the color of the interface. They decided to make the USB 3.0/superspeed USB standard devices adopt blue as the color matching of the interface plastic board to distinguish them from the old standard interface. People celebrate for a time. Even if they are short-sighted, they can recognize which interface standard is updated faster. Although the downstream hardware manufacturers feel pain when they see that there are five more pins in the connector, they bite their teeth on the new interface, and the promotion effect is worth the increase in cost compared with the cost.

Forcibly divide USB 3.1 into two generations and convince me

However, the good times did not last long. In 2013, Intel twisted the two data streams of the thunderbolt interface into one, reaching the transmission rate of 20gbit / s. usb-if looked at you, the speed was four times that of me, and I felt unbearable. In July of that year, the USB organization published the USB 3.1 standard. According to the usual logic, USB 3.1 is the upgrade of USB 3.0, but it is an untenable topic to discuss whether USB 3.1 is faster than USB 3.0 or what other progress exists today, because USB 3.0 does not exist in the definition of usb-if. Among the remaining current standards, in addition to the hi speed USB representing the 2.0 standard, there are only superspeed USB and superspeed USB 10Gbps.

Analysis and summary of USB interface standard

Is the USB 3.0 standard, which has ruled the peripherals and mobile storage connection industry for several years, suddenly declared dead? Obviously not, but the naming habit of usb-if is too bad. You should have just seen that usb-if also calls USB 3.0 superspeed USB, so it seems that this superspeed 10Gbps is USB 3.1? Naive. When the two brothers USB 3.1 Gen 1 and USB 3.1 Gen 2 come on stage, what you want to do most is to press the head of the person in charge of naming in usb-if into the display. The so-called USB 3.1 Gen 1 is the original USB 3.0. The real new standard is this thing called USB 3.1 Gen 2. As for the English name of the transmission rate, although usb-if likes it very much, we still choose to ignore it.

From the perspective of paper data, the USB 3.1 Gen 2 standard doubled the theoretical transmission rate, caught up with the first generation thunderbolt, increased the coding bit width from 10 bits to 100 bits, and reduced the signaling overhead from 20% to 3%, which is a great progress. However, this time, the downstream manufacturers quit when facing the cost and compatibility challenges brought by accepting the new standard, so they would rather “upgrade” USB 3.1 with the naming mask of USB organization than make great efforts to apply the new interface. So now the vast majority claim to support the “USB 3.1” standard, but refuse to explain whether it is Gen 1 or Gen 2 electronic products or PC accessories. In fact, it is still the ability of USB 3.0.

Analysis and summary of USB interface standard

You almost thought USB type-C = USB 3.1

In order to adapt to different types of devices, before the emergence of USB type-C, the USB 2.0 standard interfaces were divided from the interface form. There were five types of USB type-A, USB type-B, MINIUSB type-B, microusb type-A and microusb type-B (excluding those that had been eliminated). In the USB 3.0 era, USB 3.0 type-A, USB 3.0 type-B and microusb 3.0 type-B also appeared. USB type-A, USB 3.0 type-A and microusb type-B are the most frequently exposed in our daily life. Because of the dual distinction between color and shape, people can easily identify the purpose and speed of the interface.

However, in 2014, USB if released the definition of USB type-C version 1.0. This interface not only defines a new interface form that will not be inserted reversely, but its 24 contacts far exceed the 4 or 9 defined in the current USB standard. Therefore, even though USB type-C can accommodate the old standard in the form of transfer, it is not an interface for the purpose of adapting to the current USB standard, This interface is for the future. Because USB type-C almost appeared with the front heel of USB 3.1, and no one cared about the type of USB interface they plugged in and out every day, many people lost instantly and confused the two.

However, the actual situation is that USB 3.1 Gen 2 is only a transmission standard, and USB type-C is only a suitable physical carrier for it. USB type-C can also carry USB 2.0 and USB 3.1 Gen 1 protocols. Now more and more smart phones using USB type-C as interface are good examples. However, USB type-C can do much more than transmit small movies at a high speed of 10Gbit / s: USB type-C supporting USB PD 2.0 can supply power to large households such as notebooks with a high power of 20V / 5A (100W); USB type-C supporting DP additional mode can be externally connected with a display compatible with this mode; Intel even chose to share the interface with USB type-C in the definition of the third generation thunderbolt standard.

Three sentences to clarify USB standard chaos

Now you can summarize the full text in a few simple sentences:

1. USB 3.0 interface is usually blue, and there must be more than 5 contacts, while USB 2.0 interface will not have more than 5 contacts;

2. USB 3.1 GEN1 means USB 3.0 has changed a vest;

3. Don’t think USB type-C will be faster when you see it. Please recognize USB 3.1 Gen2.

Although the final direction of USB must be USB type-C / USB 3.1 Gen2, the popularization of a new standard and new interface will take at least several years. In the future, we will face the chaotic scene of the coexistence of new and old standards. We will first take preventive measures. When we contact devices with USB interface in the next few years, we can know it and refuse to be cheated.

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