How a USB hub works? How can 1 USB carry the bandwidth of 5 or more? Wouldnt it be split?
In: Technology
The bandwidth is determined by the single plug on your computer and a hub shares that bandwidth. It doesn’t split it evenly between the 5 or so hubs but imagine it’s an available pool of bandwidth that cannot exceed a specific draw over multiple devices.
It is split, but most usb devices don’t actually have high enough bandwidth for that to matter.
Devices like mice and keyboards and stuff like that barely need any bandwidth at all.
USB 2.0 has a max bandwidth of 480 Mbit/s which is enough for almost anything that used it many times over.
Modern USB 3 /USB-C can have between 5 and 20 Gbit/s depending on the version and future versions of USB will have more.
This is more than enough to handle any I/O a regular computer might want.
The bandwidth isn’t shared equally between all devices, so a mouse or keyboard will not take the same share of the total bandwidth as an SSD or an Ethernet connection via USB.
One limitation is that a single controller can only talk to up to 127 devices and is you are daisy chaining usb hubs a lot of that will be taken up by the hubs themselves as there may be several hubs hidden within one physical casing. (For example a 7-port usb hub is usually just two 4 port hubs plugged into another in a single case and counts as two device by itself.)
Another limitation is the fact that the host computer will talk to each device one at a time and can’t be permanently talking back and forth with all devices, but that isn’t really an issue for most use cases.
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