Why is USB 3.0 Not as Fast as You Think?

Have you ever encountered varying speeds on the same external hard drive using the same USB port?

One day, we decided to repurpose a 500GB mechanical hard drive from a certain laptop, which had a slow 5400RPM rotational speed – a clear relic in terms of performance.

However, with a focus on recycling, the 500GB capacity still seemed appealing. We placed it into a USB 3.0 external hard drive enclosure from the same brand and created a functional external hard drive.

Connecting it via USB and formatting it might seem like the end for most people. Yet, with experience testing numerous SSDs and portable solid-state drives (PSSDs), we felt nostalgic for this “ancient” device.

So, we decided to run it through Crystal Disk Mark, and the results left us astonished. The read and write speeds were a mere 42.78MB/s and 40.86MB/s.

Even modern USB drives don’t typically perform at such a low level, right?

Discovering that it was running at USB 2.0 speeds on a USB 3.0 port was bewildering. While this mechanical hard drive’s performance was indeed lackluster, it was at least stable. Could it be due to the cheap chipset in the enclosure or false advertising?

With a sense of skepticism, we unplugged the USB data cable, waited for the hard drive to fully stop spinning, and then reconnected it.

Running the test again yielded entirely different results, with read and write speeds of 82.19MB/s and 80.89MB/s.

Next, we tried a 1TB hybrid hard drive from the same brand in the same enclosure and conducted the test. The read and write speeds came in at 125.34MB/s and 123.96MB/s, which aligned with our expectations. It seemed that the enclosure was not the issue.

So, why does USB 3.0 mobile storage often fail to reach its advertised speeds? The culprit is often the USB connector not being fully inserted.

You might wonder why USB 3.0 is so finicky when older USB drives worked even when partially inserted. Well, USB 3.0 is indeed particular in this regard.

Let’s examine the construction of a standard USB 2.0-A connector, which reveals four relatively long contact pins inside, with only four wires in the cable.

Being an older interface, its maximum bandwidth is just 480Mbps, or roughly 60MB/s. Thus, our initial test results were in line with USB 2.0 speeds.

Now, let’s take a look at the USB 3.0-A connector (now referred to as USB 3.2 Gen1 and Gen2).

Though it looks nearly identical to USB 2.0-A on the outside, a closer inspection reveals a significant difference.

It contains two sets of contact pins: an outer row of four and an inner row of five, making a total of nine pins.

Here’s the critical part: if this connector isn’t fully inserted, only the front four contact pins connect with the socket, resulting in a USB 2.0 connection.

When fully inserted, all nine pins make good contact with the socket, enabling USB 3.0 operation with a bandwidth of up to 5Gbps, or around 640MB/s – which explains why our second and third test results matched USB 3.0 expectations.

When using USB 3.0 mobile storage, it’s crucial to identify the correct port on your PC. Typically, USB 2.0 ports have black plastic insulators inside, while USB 3.0 ports are blue.

However, this isn’t always absolute; some devices might have black USB 3.0 ports, while others could be red, yellow, and so on.

In conclusion, to fully experience the high-speed potential of USB 3.0, your mobile device and interface speed must match.

Additionally, not fully inserting the USB connector will prevent you from enjoying USB 3.0‘s high-speed capabilities.

Finally, remember that if your motherboard lacks the USB 3.0 controller driver, the interface will only function as USB 2.0. Have you learned something new today?