How to identify USB cables?

October 7, 2007 7:58 AM

I have about a million USB cables. How can I tell which ones are USB2 and which are USB1, and is there really a difference?
posted by nowonmai to computers & internet (8 comments total)

The USB 2.0 Myth.
posted by niles at 8:00 AM on October 7, 2007 [1 favorite]

I have some dollar store cables that do not work at USB 2.0 speed; connected devices, after erroring out, fall back to USB 1.0 speed (or lock up, depending on how poorly they're built). This is in linux, I don't know if windows would fall over or not in this case.

I would simply test them with something like an external hard drive, move a lot of data back and forth, and see if there's too many errors. Not sure how seeing the errors would work in windows, but I'm certain someone will suggest a way.
posted by shepd at 8:10 AM on October 7, 2007

unless you have old usb cables that has little bulging plastic things near the connectors ..(like older generation scanners that comes with..)

you should be o.k... almost all recent (since few years ago) are USB 2.0 even if it doesn't say so..
posted by curiousleo at 10:34 AM on October 7, 2007

niles has got it. The cables are theoretically supposed to be identical, but due to its slower speed, USB 1.1 isn't as sensitive to non-spec cables.
posted by spiderskull at 11:25 AM on October 7, 2007

What's the deal with the bulgy things on older cables?
posted by nowonmai at 12:17 PM on October 7, 2007

nowonmai: They are ferrite beads
posted by smcniven at 1:13 PM on October 7, 2007

The cables are theoretically supposed to be identical ...

Not quite true. The USB 1.1. spec says a maximum length of 3m; USB 2.0 spec says maximum of 5m. IIRC the original, never-widely-adopted, USB 1.0 spec said a maximum of 850mm.

There's a whole lot more to it than that, mostly to do with propagation delay and signal rise/fall times (both related to cable reactance) and allowable device response time, but what it boils down to is this:

• If it's got a ferrite suppressor on it, it's definitely USB 1.1 (or, just maybe, USB 1.0)
• If it's between 3 ~ 5 metres, it should be a USB 2.0 cable (notwithstanding dodgy manufacturers making 'long' USB 1.1 cables)
• If it's < 3m long, treat it as a USB 1.1 cable - though you might be able to get it to work at USB 2.0 speed if it doesn't have a ferrite suppressor, particularly as long as you don't daisy-chain devices or hubs.

posted by Pinback at 7:10 PM on October 7, 2007

Thanks folks. All the cables are less than 3m, and I forgot to say that I am using a Mac, but I have learned a lot and can throw out the ones that won't give me a 480Mb/s connection to my device.
posted by nowonmai at 7:30 PM on October 7, 2007