If you own a desktop computer, the number of USB ports at your disposal might be an embarrassment
of riches. Even mid- to low-range machines can offer more USB than you could possibly know what
to do with. But is it actually a good idea to use them all at once? Here's the deal. You know how
the makers of USB products like to loudly yell about how blazingly fast they are? Well, it's
fairly common knowledge in the tech world that those advertised numbers are theoretical
maximums that you probably won't see in reality. And using multiple USB ports at once can actually
cut into these speeds even further due to a separate effect. You see, your computer's USB ports are
connected to controller chips inside the system, and a single USB controller can only handle so
much traffic. So let's say you have two USB 3 ports on the front of your computer connected to a
header on the motherboard that utilizes one controller. You can get the full five gigabits
per second if you're just plugging one flash drive into those ports. But if you're using both,
then those two drives actually have to share that five gigabits of bandwidth. So if you're
moving data on both ports simultaneously, the theoretical maximum speed per port will be cut
in half. And this isn't just true for front panel inputs. Oftentimes, the ports on the back of your
PC, which don't even use a header cable, are susceptible to the same problem. It just isn't
all that common for a port to have its own dedicated controller utilized by nothing else.
So why not one controller per USB port? Well, think about how most people use their USB ports.
You'll have a flash drive to transfer data every now and again, but your other ports are
probably being pressed into service for your keyboard, mouse, headset, or novelty glitter lamp.
And none of those things requires very much bandwidth. Given then that the vast majority
of users aren't constantly blasting data down multiple USB ports at once, there just isn't
much reason to build a bunch of controllers onto a typical motherboard. But most systems do have
more than one USB controller. If you go into Windows Device Manager, you'll typically see
multiple devices that are labeled USB host controller. So it's not like you have eight or
12 ports that are all sharing one pipe. However, do keep in mind the limits of a single controller
if you're doing something heavy, like editing video and constantly backing up footage or
using a VR headset with your PC. In fact, Oculus officially recommends connecting no
more than two of their sensors to a single USB controller due to how much data needs to be
processed for a smooth VR experience. This is not just due to possible bandwidth issues,
but also due to the logic of the controllers themselves becoming overloaded.
And keep in mind that a similar concept applies to the way that USB handles electrical power.
If you're trying to charge or power multiple devices from your computer,
each device won't get the full amount of power if many of them are connected to the same internal
hub. So you could see slower operation if you're using an older mechanical external hard drive or
a couple of those novelty fans to cool you down because you spent all your money on a graphics
card and didn't have enough leftover for an air conditioner. So if you have a lot of USB devices
that you need to use at once, think carefully about how much data they'll be moving and also
do some digging to see how many host controllers your computer comes with. I know that, yes,
theoretically you can connect 127 devices to a single USB controller, but I wouldn't recommend
trying that unless you have a very good reason. Just like I'd recommend subscribing,
because you have a great reason. These videos are great. Get subscribed.