Discussion USB 3.0 / USB-C cable length versus throughput

[mikeymikec]

I sold a customer a Crucial X6 external SSD which came with a USB-C to USB-C cable which was about 10-20cm long at most. Out of curiosity I did a quick throughput test on it and got about 500 megabytes/sec out of it. As the customer plans to work with the drive while sat in their armchair, I suggested a longer USB-C cable. I had a couple of Anker USB-C to USB-C cables with me which looked about 2m in length, but at best the throughput test came out at about 50 megabytes/sec.

From the official spec:

(https://www.usb.org/sites/default/files/USB Type-C Spec R2.0 - August 2019.pdf)

I've been aware of USB 2.0's 5-metre limit for many years but I hadn't realised that the cable lengths have been getting shorter with each successive standard.

I guess I'm going to have to go on the hunt for USB 3.0 / C cables that are actually worth a damn in throughput terms. I'm also kind of amazed that one can buy a USB-C cable (which I would have thought would be considered firmly in the realm of USB 3.0 and later in terms of throughput) and only get USB 2.0 throughput out of it (I am also aware that there are charging-only cables both lately and historically).

 

[mindless1]

Were these plugged into a motherboard rear USB port, or a case port, or external hub? Just wondering if it might be a case of the sum of degradations, though of course it could be as simple as the Ankers being electrically conductive to the standard but insufficient shielding or wire gauge.

I do have several USB3 cables that came with things like external HDDs, around 1M long that routinely reach ~150MB/s which I had just assumed was a limit of the HDD itself. A few are even plugged into a couple unpowered (USB cable powered not external PSU) USB3 hubs with their own USB3 cable about 50cm long, plugged into mobo rear USB ports.

Those cables aren't particularly beefy looking, but then they are 5.25" HDDs with external AC/DC adapters, so don't depend on the cable for power delivery.

At the same time, this review states the X6 only consumes 340mA under load which is not much for a 2M cable to handle:

Crucial X6 2TB Portable SSD Review Practical testing

www.ocinside.de

Let us know if you find particularly good performing, long USB3 cables!

 

[In2Photos]

Thanks for pointing that out. Not sure I have ever realized that. I have a 1TB Samsung T7 that I just tested out. Plugged into the native USB-C port on a Dell dock connected to my Dell XPS15 via Thunderbolt.

With the ~18" cable that came with the drive.


With a 36" cable I had laying around (could be a "charging cable")


With a 6' USB A to C cable in a USB 3 port (this must be a USB2 cable)


With a 6' USB3 cable.

 

[mikeymikec]

Were these plugged into a motherboard rear USB port, or a case port, or external hub?

Laptop

 

[Tech Junky]

When testing the highest throughput is limited to cables under 3.3ft. Once you go beyond that the signal needs a boost to get to the higher numbers. It's as simple as that.

When I was testing TB cables they all fell within a margin of the top speeds even though some cost $40 while others came in under $20. Price isn't a good indicator but, if it's dirt cheap it's probably not going to work as expected or desired.

$33.99	Anker (TB3)
$28.99	Cable Matters (TB4)
$24	OWC (TB4)
$15.83	Sniokco (USB4)
$13.99	Monoprice (USB40)
$13.93	Accell (USB40)
$11.99 w/ 50% Coupon	Ibvanky (USB40)
2 @ $12.99	B094FSGDPY - 6,6 ft

https://www.amazon.com/gp/product/B0B2LXZ758 - I use this 8 footer for P2P with my server and it links at 20gbps which is expected due to the protocol but, at nearly 10ft it allows me to sit away from the server vs using one of the shorter cables above. I tested a couple of other long cables like this one but went back to the trough for a cheaper option as the other were double the cot for the same performance.

USB cables aren't held to a strict tolerance like TB. That's where you get into the "charging" "usb 2 - C" options. Like most phones you get USB2 data speeds out of them due to wanting to push higher than spec voltage for charging. One Plus is one of them because they unleash 100W charging for recent phones where others are still playing around with 20-30W chargers that take all day to charge the battery. I'll take 100W charging though and just move data over WIFI instead of 480mbps over the cable.

 

[mikeymikec]

Yep, searching for 'thunderbird cable' yields much more relevant results if one is looking for high data transfer speeds.

 

[mikeymikec]

An interesting development on this topic - when backing up a 128GB file from my laptop today, I wanted a bit more throughput than my flash drive gives, so I hooked up my USB-C NVMe M.2 adapter with an Amazon Basics USB A-to-C 3-metre cable and got a consistent 300MB/sec write speed out of it.

The source SSD is an old M.2 SATA drive so it's an obvious performance cap, but still, that's a lot better than the Anker cable I used when I wrote the OP.