What issues are there with long USB cables?

Quartz · 20 Feb 2019 at 10:55

I've been very pleased with my fibre-optic Displayport cable and it occurs to me that by using long cables I could put my PC a lot farther away (cable-length-wise) and thereby reduce noise. The basic idea would be to have fibre DP cables going to my monitors and one 5m USB 2 cable going to a USB 2 hub and one 5m USB 3.0 cable going to a USB 3.0 hub.

I don't have any USB 3.1 / 3.2 peripherals.

Of which issues should I be aware?

LuckyBenski · 20 Feb 2019 at 13:04

Maximum recommended length for USB 3 is 3m and it's 5m for USB 2. USB 3.0 was relabelled USB 3.1 gen 1, USB 3.1 has been relabelled USB 3.1 gen 2.

I would say a 5m quality cable can work for USB 3 but it depends on usage. For a peripheral or two, long cables might be ok. Anything that draws power will create more issues as longer wires will have a greater voltage drop and so eventual latency. A powered hub on the end would probably help.

YMMV greatly but I'm interested to know how it goes. I looked into all this and compromised on two individual extensions for keyboard and mouse, but it's bulky.

Quartz · 20 Feb 2019 at 13:15

The expense would be considerable - the Displayport cables are £179 each. Plus tax. (And if you think that's expensive, take a gander at USB 3.x fibre cables.) So I'm looking at a bill of ~£400. Thus I'm trying to do some research first!

LuckyBenski said:
Anything that draws power will create more issues as longer wires will have a greater voltage drop and so eventual latency.

Both USB 2 and USB 3 cables will go from the PC to powered hubs.

Quartz · 20 Feb 2019 at 20:08

And I'm going to have to buy a long TOSLINK cable for my headset too.

Hmm... how much bandwidth am I going to need? Going through USB 2 I'll have a max of keyboard, trackball, headset, and HOTAS. I'll keep USB 3 for my phone and any external HDD.

LuckyBenski · 20 Feb 2019 at 21:06

Quartz said:
And I'm going to have to buy a long TOSLINK cable for my headset too.

Hmm... how much bandwidth am I going to need? Going through USB 2 I'll have a max of keyboard, trackball, headset, and HOTAS. I'll keep USB 3 for my phone and any external HDD.

I'd worry about 40 devices and related interrupts etc. I wouldn't even like to use those all on one port at all. But really I think you'd have to try it and see.