Not all USB ports are the same, and the easiest way to tell them apart is by the color codes that indicate their generations — for USB-C, markings show the underlying standard and capabilities. For high-performance devices like a USB thumb drive or an external SSD, I recommend using USB 3.0 or USB4 ports to get maximum speed.
However, despite their speed, these ports come with a significant trade-off nobody tells you about.
USB 3.0 and later ports and devices generate high-frequency electromagnetic noise that can interfere with nearby 2.4GHz devices connected through other ports, such as peripherals or Wi-Fi and Bluetooth adapters, potentially disrupting their signals and slowing them down.
Your USB 3.0 and newer ports are jamming your wireless adapters
Port placement makes this worse
USB 3.x ports are incredibly fast and run on high-frequency signals. Specifically, ports and devices that support SuperSpeed run at 5Gbps.
Now, most wireless peripherals and adapters, like Wi-Fi and Bluetooth, share the same 2.4GHz frequency, and noise from newer ports and cables can disrupt their radio signal. When this happens, you might experience frequent signal drops and hitching when using the peripherals or adapters.
Motherboard manufacturers place most USB ports together, and that’s been the practice for as long as desktop computers have existed. If they do anything different, the placement will look awkward, and multiple ports stacked together make up for convenience. Initially, it didn’t matter because ports predating USB 3.0 produced far less interference.
However, when multiple ports are grouped on laptops, desktops, or hubs, with USB 2.0 and USB 3.0+ in proximity, the interference worsens, and the disruption bleeds into 2.4GHz devices, causing frequent slowdowns. Intel first revealed this issue in 2012, yet it can still affect your device some 14 years later.
USB4 raises that to 20Gbps or 40Gbps over USB-C, creating even higher-frequency signals, though it also features better shielding than USB 3.x. As USB4 wasn’t available at the time of the original research, there has been little to no research into this issue since USB4 launched. On that note, this problem largely affects USB 3.x configurations and devices, despite USB4’s higher frequencies.
Your ports are also splitting bandwidth behind the scenes
Two fast devices connected through a single controller can cause a slowdown
Beyond radio interference, another cause can slow down your USB port. When one USB port is being stressed, it can potentially slow down the other ports. USB devices connected through a single controller share limited bandwidth, so you aren’t guaranteed full speeds across all ports at the same time.
For instance, if you have an external SSD and transfer data through a USB 3.1 or USB-C port, it might saturate the bandwidth available to that controller. With USB4, the same bandwidth issue persists, and since it can carry video too, that bandwidth is taken away from the other ports connected through the same controller.
The bandwidth apportioned to each controller is divided across the ports, regardless of USB generation. So, pushing the load on the other port connected through the same controller can split the bandwidth across both devices, so neither will reach the advertised full speeds.
However, it really depends on the motherboard’s topology, including how ports are partitioned between controllers and which ports share the same controller. For the most part, USB ports sharing the same controller are stacked next to each other. Here’s how to fix both these problems
A simple port swap is all it takes
The best way to tell you’re experiencing a radio frequency slowdown is that, when stressing devices connected via USB 3.0 and newer ports, you’ll notice cursor lag, keys taking too long to register, choppy audio with wireless peripherals or your Wi-Fi lagging.
For the radio issue, the simplest fix is to switch the ports your device is connected to. I recommend leaving a considerable gap between USB 3.0 and USB 2.0 devices. Even when USB ports are stacked, some still have a gap between them; my B550 motherboard has a DisplayPort that bridges the gap between all ports, so I recommend taking advantage of such a layout if provided.
To tell if you’re experiencing a bandwidth split, high-speed devices connected simultaneously may slow down and not reach the speeds the ports are advertised for, which happens when they share the same controller.
The fix is easy. Just don’t use two high-speed devices in ports that share the same controller. USB4 ports are already limited on a computer, so check the motherboard manual before plugging a USB4 SSD and a USB 3.x device side by side. Again, there is limited research on USB4 devices and ports, but if USB 3.x is in play, it’s worth considering.
Also, different high-speed ports are scattered throughout, either on the front panel or on the motherboard, so once again, split the devices across different ports.
However, all controllers might still limit bandwidth at a certain threshold (which an average user is unlikely to hit) because the overall bandwidth allotment for USB devices isn’t unlimited either.
The fix is free, but your motherboard layout matters
For the most part, USB layouts have remained consistent across motherboards, and USB 3.x port radio interference was never really considered. This isn’t a design flaw per se, but more of a design challenge that you can easily resolve by changing the arrangement on your PC, though you’d still need to figure out your motherboard’s configuration first.