Personal computing discussed

Moderators: morphine, Steel

 
Noldor
Gerbil Team Leader
Topic Author
Posts: 200
Joined: Sun Mar 04, 2007 4:48 am

USB 3.0 cable slow speeds for a short period?

Thu Mar 30, 2017 6:12 pm

Hi, is it possible that an USB 3.0 cable to start, out of the blue, to deliver only USB 2.0 speeds and then recover on its own? Basically what happened: when transferring some files to an external drive, through an USB 3.0 port and an USB 3.0 cable, I've noticed that the transfer speeds were about 30-35 MB/s, a bit slower than what I would have expected (50-70 MB/s). This occurred twice and, at first, I did not pay attention to it, thinking the files were fragmented or something like that. But a third time, I had a feeling something was unusual. So, I tested transferring those files with another cable (using the same external drive and PC) and the speeds were 50-70 MB/s as they should have been. I tested the suspect cable twice with a different drive and a different PC and, at first, the results were suggesting it was likely faulty, giving constant speeds of 30 MB/s. I thought the cable was defective and was about to throw it away, when, merely out of inertia, I ran a third test and the speed returned to normal. I tested again the (potentially) defective cable several times and the speeds were normal.
Anyone has any idea what might be going on? I can imagine a cable being defective, but I've never heard of such a thing, a cable throttling its normal speeds and then recovering on its own out of the blue.

PS: Yes, I know a mere USB cable is worthless, and it can be easily tossed aside, but, as a matter of principle, when a piece of my equipment, no matter how insignificant, goes bad, I like to try to figure out why (that's to pre-empt advices of the sort "just replace the cable", which would miss the point).
 
just brew it!
Gold subscriber
Administrator
Posts: 49696
Joined: Tue Aug 20, 2002 10:51 pm
Location: Somewhere, having a beer

Re: USB 3.0 cable slow speeds for a short period?

Thu Mar 30, 2017 6:26 pm

USB cables vary widely in quality. While the usual behavior with a marginal cable is a simple failure of the device to detect, nothing really surprises me any more. USB 3.0 ports also vary widely in quality, so the behavior being different on another system isn't particularly unusual either.
Nostalgia isn't what it used to be.
 
Noldor
Gerbil Team Leader
Topic Author
Posts: 200
Joined: Sun Mar 04, 2007 4:48 am

Re: USB 3.0 cable slow speeds for a short period?

Fri Mar 31, 2017 2:03 am

just brew it! wrote:
USB cables vary widely in quality. While the usual behavior with a marginal cable is a simple failure of the device to detect, nothing really surprises me any more. USB 3.0 ports also vary widely in quality, so the behavior being different on another system isn't particularly unusual either.


Thanks for the feedback. One minor observation, because it seems there is a misunderstanding: the behavior of the cable was not different on a different system. It was the same, meaning that when testing it on another PC, either with the same external drive or a different one, it exhibited the same drop in speed several times (until it just recovered out of blue and started delivering the normal speeds on either systems). The USB 3.0 port which was the one I was using when I first noticed the slower speed also behaved normally when connected to different cables. So it is pretty certain (at least as much as one could be in such cases) that the USB port is fine.
 
Noinoi
Gerbil Team Leader
Posts: 228
Joined: Fri Jun 26, 2015 11:31 pm
Location: Somewhere, anywhere!

Re: USB 3.0 cable slow speeds for a short period?

Fri Mar 31, 2017 2:53 am

just brew it! wrote:
USB cables vary widely in quality. While the usual behavior with a marginal cable is a simple failure of the device to detect, nothing really surprises me any more. USB 3.0 ports also vary widely in quality, so the behavior being different on another system isn't particularly unusual either.


I've seen really strange behaviour with certain aftermarket USB 2.0 Type-A to microUSB cables, too. One I have will work perfectly fine off an AC adapter or on a USB 2.0 port, but a 3.0 port will generate errors as soon as data transfer occurs.

Kind of funny, though. How can port type influence cable behaviour?

I also have a USB 3.0 enclosure that does not like some ports on my laptop. I must use ports on the left side of the laptop (of which one of the ports is deliberately designed for charging smartphones at a high current) for it to just not endlessly repeat connecting and disconnecting, apparently due to lack of power. Desktop USB 3.0 ports work perfectly fine.
i5-4590 | Kingston 2x8GB | Asus Strix GTX 970 | Asus Z97-Pro Gamer | Kingston Fury 240GB + WD Black 2TB + Blue 2TB | Win 10 FCU

Who is online

Users browsing this forum: No registered users and 1 guest