Question:

What are the factors that prevent USB 2.0 file transfers from reaching the theoretical maximum of 480 Mbit/s, and why do I only get 6-9 MB/s when using a USB 3.0 stick on a USB 2.0 port?

Some additional sentences that could follow the rephrased question are:

– According to Wikipedia, USB 2.0 has a High Speed mode that can support up to 480 Mbit/s, but the actual throughput is limited by bus access constraints to 35 MB/s or 280 Mbit/s.

– However, in practice, there are other factors that can influence USB transfer speeds, such as cable length, cable quality, device compatibility, interference, and the type of file being sent .

– Moreover, using a USB 3.0 stick on a USB 2.0 port will result in a downgrade of the connection speed to USB 2.0 levels, as the port determines the maximum speed of the data transfer. Therefore, even if the USB 3.0 stick is capable of faster speeds, it will not be able to utilize them on a USB 2.0 port.

Answer:

Why USB 2.0 file transfers are slower than expected

USB (Universal Serial Bus) is a widely used standard for connecting and transferring data between various devices, such as computers, smartphones, cameras, flash drives, and more. USB has evolved over the years, with newer versions offering higher speeds and more features. However, many users may have noticed that their USB file transfers are not as fast as they expected, especially when using USB 2.0 ports or devices. In this article, we will explore some of the reasons why USB 2.0 file transfers are slower than the theoretical maximum of 480 Mbit/s, and why using a USB 3.0 stick on a USB 2.0 port does not improve the speed.

According to Wikipedia, USB 2.0 was released in April 2000, adding a higher maximum signaling rate of 480 Mbit/s called High Speed, in addition to the USB 1.x Full Speed signaling rate of 12 Mbit/s. However, this does not mean that the actual data transfer rate will be 480 Mbit/s, as there are several factors that limit the effective throughput. One of the main factors is the bus access constraint, which means that the USB devices have to share the bandwidth of the bus with other devices and the host controller. This can cause delays and overheads in the data transmission, reducing the available bandwidth for each device. According to some estimates, the effective throughput of the High Speed signaling rate is limited to 35 MB/s or 280 Mbit/s .

Other factors affecting USB transfer speeds

Besides the bus access constraint, there are other factors that can influence the USB transfer speeds, such as:

– Cable length and quality: The longer and thinner the USB cable, the more resistance and attenuation it will have, which can degrade the signal quality and cause errors and retries in the data transmission. Moreover, the quality of the cable connectors and shielding can also affect the signal integrity and interference. Therefore, it is recommended to use shorter and thicker USB cables with good quality connectors and shielding for optimal performance .

– Device compatibility: The USB standard is backward compatible, which means that newer USB devices can work with older USB ports and vice versa. However, this also means that the speed of the data transfer will be determined by the lowest common denominator of the devices involved. For example, if you use a USB 3.0 stick on a USB 2.0 port, the connection speed will be downgraded to USB 2.0 levels, as the port determines the maximum speed of the data transfer. Therefore, even if the USB 3.0 stick is capable of faster speeds, it will not be able to utilize them on a USB 2.0 port. Similarly, if you use a USB 2.0 stick on a USB 3.0 port, the speed will be limited by the stick’s capabilities. To achieve the best possible speed, you need to use devices that support the same or higher USB version as the port.

– Interference: USB devices can be affected by electromagnetic interference (EMI) from other devices or sources, such as power cords, wireless routers, speakers, etc. This can cause noise and distortion in the USB signal, resulting in errors and retries in the data transmission. To avoid or minimize interference, you should keep your USB devices away from potential sources of EMI, and use shielded USB cables and devices .

– Type of file being sent: The type and size of the file being transferred can also affect the USB transfer speed, as different files may require different amounts of processing and compression by the USB devices and the host controller. For example, transferring a large number of small files may take longer than transferring a single large file, as each file may incur additional overheads such as opening, closing, and verifying. Moreover, transferring files that are already compressed, such as MP3, JPEG, or ZIP files, may take longer than transferring files that are uncompressed, such as WAV, BMP, or TXT files, as the USB devices and the host controller may not be able to compress them further and save bandwidth .

Conclusion

USB 2.0 file transfers are slower than the theoretical maximum of 480 Mbit/s due to various factors, such as bus access constraints, cable length and quality, device compatibility, interference, and type of file being sent. These factors can reduce the effective throughput of the USB 2.0 High Speed signaling rate to 35 MB/s or 280 Mbit/s, or even lower in some cases. Moreover, using a USB 3.0 stick on a USB 2.0 port will not improve the speed, as the port determines the maximum speed of the data transfer. To achieve the best possible USB transfer speed, you should use devices that support the same or higher USB version as the port, and use high-quality cables and devices with minimal interference. I hope this article was helpful and informative for you. Thank you for reading. 😊