When testing the USB3.0 Portable storage device, we found a strange phenomenon: if the USB3.0 device is slowly inserted or inserted into the USB3.0 port in segments (the so-called segment insertion is to insert a small part, pause slightly and then insert it completely)

The burst transmission speed of the USB3.0 Portable storage device detected by HDD Tap is actually the speed of USB2.0 (about 35MB/s). After verification on various motherboards using NEC, ASMedia USB3.0, and chips, this phenomenon occurs. Why is this?

After carefully studying the wiring definitions of USB2.0 and USB3.0 and conducting multiple experiments, the truth finally came to light. Let's take a look at the reasons together:

Looking at the appearance of USB2.0 and USB3.0, let's first take a look at the pin definition of USB2.0. There are four signal wires:

Let's take a look at the pin pin definitions of the USB3.0 male and female ports again:

From the above figure, we can see that the definition of 1-4Pin in USB2.0 is consistent with USB3.0, except for the addition of 2 pairs of TX, RX signal wires, and 1 Gnd wire. The 5 Pin pins in the latter part are the key Pin pins in USB3.0.

When inserting a USB3.0 device into the USB3.0 female port on the motherboard, the 4 pin (USB2.0) signal wire on the front end of the male port will first contact the 4 pin (USB2.0) signal wire on the female port, followed by the 5 pin signal wire.

If the system detects the equipment for a short time, if we have not yet connected the rear 5Pin (USB3.0) signal line, the equipment will be judged as a USB2.0 equipment by the system, that is, the equipment insertion time>the time when the System identification the equipment, then the USB3.0 equipment will be recognized as a USB2.0 equipment by the system in advance. The equipment insertion time refers to a very short period of time from the beginning of equipment insertion to the connection of the rear 5Pin signal line.

Question: The device only started to plug in a bit slowly, but in the end it was completely plugged in. Why is the device still recognized as a USB 2.0 device? This is because after the system detects the device as a USB2.0 device, when the USB2.0 pin pins of the male and female ports come into contact, the device detection is not restarted. We only need to restart the OS or disable the USB3.0 Controller in Device Manager, and then enable the USB3.0 Controller. After this operation, we can verify the burst transmission speed by running HD-Tach, which can reach over 100MB/s. Actual measurement: This is just measured by a small editor. The same compressed file is transferred. The USB3.0 Portable storage device is inserted slowly:

　　这是快速插的：