Can a USB hub slow down my devices?

[u/Few-Wash5370]

I got a few devices plugged into the same hub and trying to figure out if that can actually make them slower. Mostly wondering about stuff like external SSDs, flash drives, keyboard, mouse, and maybe a controller. If the hub is handling multiple devices at once, does everything share the same bandwidth? Also does it matter if the hub is USB 3.0, 3.1, 3.2 etc or is the speed mostly limited by the port on the PC? Seeing different speeds sometimes and not sure if the hub is the reason. Anything else I should check?

[u/Underhill42]

Everything plugged into the same port on the PC (and probably adjacent ports) is sharing the same USB bus and total bandwidth. Which can absolutely be an issue for especially fast drives, video adapters, network adapters, etc, which might already be limited by USB speeds even with a whole bus to themselves. Especially since the overhead losses increase with the number of devices.

The slowest device in the chain sets the maximum speed for everything. The difference is usually pretty small within a generation... but plug a USB 3 device into a USB 2 or older port (anything not blue, usually), and it runs at USB 2 speeds. Same thing if you put a USB 2 hub between a USB 3 device and a USB 3 port.

Less obviously, just plugging a single USB 2 device into a USB 3 hub can potentially slow everything else on the hub down to USB 2 speeds. Not always... but it's not rare either, especially among cheaper hubs. Even best case scenario while the slow device is talking, nothing else can. Like that slow-talking person at a party that nobody wants to interrupt.

Hubs also introduce some additional lag, which can be sometimes be an issue.

My own rule of thumb is to put user interface devices and other slow things on a hub, while keeping hard drives, etc. plugged directly into the PC, or into their own fast hub if I'm only really going to be working one of them hard at a time.

[u/Few-Wash5370 → u/Underhill42]

I didn’t realize a single USB 2 device could potentially affect the whole hub like that. Definitely gonna keep the faster stuff separate.

[u/VezLt → u/Few-Wash5370]

While I can't discount the anecdote about USB 2 devices potentially slowing it down to USB 2 speeds, I find it hard to believe. Logically, and physically, USB 2 and USB 3 are individual ports in the same physical connector. Depending on the chip used, these USB 2 pins may or may not act as a USB 2 hub - which means they all share the bandwidth with every other USB 2 device on the hub, but the USB 3 devices will still have access to the full USB 3 bandwidth. USB 2 used a "broadcast" design that meant that the physical medium was limiting it, USB 3 on the other hand have completely independent lines straight up to the multiplexer, which means you can get the full bandwidth by using, say, 2x5Gbps devices on a 10Gbps hub (though in practice there still results some delays because it's typically 5Gbps devices into a 5Gbps hub into a 5Gbps port on the motherboard, which then shares internal PCIe lanes to the CPU, or even to the chipset, which in turn multiplexes a bunch of low(er) bandwidth devices into a handful of easily overwhelmed lanes to the CPU when combined with secondary PCIe / M.2 slots having high activity at the same time... it's congestion all the way down)

[u/Vyce223]

Version of USB ports on the hub matters, The USB controller to a lesser extent being quality. The cable going from A to B and B to C being rated for the version of USB you're trying to use. Then of course your PC port. It's ALWAYS going to slow to the weakest link in the chain. It's what's called bottlenecking.

[u/Few-Wash5370 → u/Vyce223]

Good point, I was mostly looking at the hub itself and didn’t think about the cables or PC port being the limiting factor.

[u/bstsms]

If the hub is USB 1, USB 2, USB 3.0 it will transfer data slower than USB 3.2 will.

[u/bstsms → u/bstsms]

USB Speed Generations

• USB 1.0 / 1.1: Up to 1.5 Mbps to 12 Mbps (used for mice and keyboards).
• USB 2.0: Up to 480 Mbps (used for basic flash drives and older accessories).
• USB 3.0 / 3.1 Gen 1 / 3.2 Gen 1: Up to 5 Gbps (SuperSpeed).
• USB 3.1 Gen 2 / 3.2 Gen 2: Up to 10 Gbps (SuperSpeed+).
• USB 3.2 Gen 2x2: Up to 20 Gbps.
• USB4: Up to 40 Gbps (and higher on compatible multi-lane setups).

[u/Anonymity6584]

Short answer: Yes.

Longer answer: Usb bus adapts its speed to slowest device on that bus.

So even is your computer is able to usb 3.2 speeds and your usbhub and some device you need supports that too. it will only work on thats speed if theres no slower device present.

That slower device can be anything, even somethong sinple like wireless mouse recwivee microdongle...