75

Does a USB 3.0 connection require a USB 3.0 cord to reach USB 3.0 speeds (SuperSpeed)? Will any USB cord support any USB 3.0 device?

93

The SuperSpeed transfer mode requires a USB 3.0 or higher cable. Earlier cables will still make a connection at a slower rate.


Source 1: USB 3.0 - Wikipedia

The VBUS, D−, D+, and GND pins are required for USB 2.0 communication. The additional USB 3.0 pins are two differential pairs and one ground (GND_DRAIN). The two additional differential pairs are for SuperSpeed data transfer; they are used for full duplex SuperSpeed signaling.


Source 2: USB 3.0 Super Speeds - USRobotics

USB 2.0 cables can be used with 3.0 ports but the transfer rate will fall back to 2.0


Source 3: Are USB 3.0 cables different? - Answers - UserBenchmark

Yes, to get USB 3.0 speeds, you need special USB 3.0 cables. Yes, USB 3.0 cables are different. Even though you can connect a USB 3.0 device via a USB 2.0 cable, in order to achieve full USB 3.0 speeds you need to re-wire any existing cabling. USB 3.0 cables are generally thicker because they have nine internal wires versus four on USB 2.0 cables.

  • 1
    Is there any substance in the "usually blue" claim? – Martin Argerami Jul 7 '15 at 23:33
  • 21
    @MartinArgerami The usually blue applies to the plug (not the cable) - "Since USB 2.0 and USB 3.0 ports may coexist on the same machine and they look similar, USB 3.0 specification mandates appropriate color-coding and recommends that the Standard-A USB 3.0 connector has a blue insert (Pantone 300C color). The same color-coding applies to the USB 3.0 Standard-A plug" – DavidPostill Jul 8 '15 at 0:44
  • 2
    There's a semi-official colour scheme I've noticed with sockets - USB 3's blue, USB 2.0 charging connectors (which are powered even when the PC they are off) are sometimes yellow. I'd rather look at the connectors for identification since I have blue usb 2.0/1.1 cables. – Journeyman Geek Jul 8 '15 at 4:16
  • 3
    I understand that it's a quote, but I think that “will fall back...” should really be “will not magically increase”. – Carsten S Jul 8 '15 at 8:13
  • 2
    For completeness, it's worth mentioning that 10GB USB3.1 ports (twice as fast as the 3.0 standard) are commonly a lighter shade of blue. I don't know if this is an official recommendation or not; but has held with most of the 3.1 board prototypes I've seen so far. – Dan Neely Jul 9 '15 at 0:49
57

A "USB 3.0 connection" requires a USB 3.0 cable.

Some USB 3.0 devices can be connected and operated as a USB 2.0 device (at USB 2.0 speeds), using a USB 2.0 cable. However, speed is not the only issue.

There are at least three important differences in cable construction between the two standards.

Related to speed:

  • The USB 3.0 cable has 9 internal conductors vs. 4 in USB 2.0.

    Four of the nine match the USB 2.0 configuration (two are for power and two are for signal). Connecting a USB 3.0 device with a USB 2.0 cable uses those conductors and operates like a USB 2.0 device.

    The other five are signal conductors, which are used for the communication method that provides USB 3.0 "superspeed" (a good general description can be found here).

  • USB 3.0 cables have a limit of 3 meters vs. the USB 2.0 limit of 5 meters.

    (Note that this is a practical limit. The cable can be any length as long as it meets all of the electrical requirements in the specification. The 3 meter limit is based on maximum allowable losses using the largest recommended wire size so that the cable is flexible.) source: specs

Related to power:

  • A USB 2.0 cable may not be adequate for a high current USB 3.0 device.

    Some USB 3.0 devices draw more power than USB 2.0 devices. The power conductors in USB 3.0 cables need to be able to carry 900mA instead of 500mA for USB 2.0.


Additional information on USB 3.0 vs. 2.0 can be found here.

  • 1
    yep, it works with legacy USB speeds using legacy cords. – Francisco Tapia Jul 7 '15 at 15:42
  • 1
    @arielnmz: To achieve USB 3 speeds, the specs define the performance characteristics the wire needs to meet. I'm not familiar with whether UTP could meet the requirements, but the spec is here: intel.com/content/dam/doc/technical-specification/… – fixer1234 Jul 7 '15 at 16:13
  • 3
    And note the reverse on power: I have a USB2 device that draws too much power, it originally had a two-headed cable that let it draw power from two ports at once. Now it's fed from a single USB3 port with no gripes about drawing too much. – Loren Pechtel Jul 7 '15 at 21:31
  • 2
    @Bilo: If you plug it into a USB 3 port it should work (a USB 2 port limits the current output to 500mA). But that's a waste of a USB 3 port. You would be better off getting a USB 3 enclosure for the drive and taking advantage of 10x the speed. – fixer1234 Jul 11 '15 at 3:44
  • 1
    @JosephRogers, you're right. The USB port will be a bottleneck as long as it's slower than the peak transfer rate. You don't need to saturate it; performance will be degraded if the peaks exceed the bandwidth. On a good hard drive, that can be several times the USB 2.0 limit. With a good drive, you can benefit from USB 3.0's 10X speed, but you won't realize 10x the transfer rate. That was poor wording in my comment. – fixer1234 Oct 3 '18 at 16:32
12

USB 3.0 jacks will work with older USB 2.0 cords, but at USB 2.0 speeds. The newer USB 3.0 connectors have more wires to carry the higher data rate.

  • 2
    Is it the same with USB 1 cables? Will USB 1 cords work in a USB 3 jack at USB 1 speeds; or will they not work at all? – user568458 Jul 7 '15 at 15:50
  • 1
    @user568458 - USB 2.0 is backwards compatible with USB 1.0 and USB 1.X cables and devices. Since USB 3.0 devices plugged into a USB 2.0 port will act like a USB 2.0 device this means a USB 3.0 device when plugged into a USB 1.0 or 1.x port will act like a USB 1.0 or 1.x device. – Ramhound Jul 7 '15 at 16:26
  • 2
    @user568458 All USB cables were identical before USB 3.0. – gronostaj Jul 10 '15 at 8:58

protected by Community Jul 7 '15 at 20:23

Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged or ask your own question.