如果您對USB3.0還不熟悉，那麼您可能會對支援USB3.0的裝置可以和/或應該使用的電纜有很多疑問。有鑑於此，今天的超級使用者問答帖子幫助好奇的讀者瞭解USB3.0的“來龍去脈”。

今天的問答環節是由SuperUser提供的，SuperUser是Stack Exchange的一個分支，是一個由社群驅動的問答網站分組。

照片由肖宗宗提供（小宗宗–Flickr）。

問題

超級使用者讀者Xavierjazz想知道USB 3.0連線是否需要USB 3.0電纜才能達到其全速潛能：

Do USB 3.0 connecti*** require USB 3.0 cords to reach USB 3.0 speeds? Will any USB cord support any USB 3.0 device?

USB3.0連線是否需要USB3.0電纜才能達到其全速潛能？

答案

超級使用者貢獻者Steven和fixer1234為我們提供了答案。首先，史蒂文：

A USB 3.0 cable is required for USB 3.0 speeds, but any USB cord will make a connection.

Source 1: USB [Wikipedia]

SuperSpeed (USB 3.0) is supported only by USB 3.0 and newer interfaces, and requires a connector and cable with extra pins and wires, usually distinguishable by the blue inserts in connectors.

Source 2: USB 3.0 Super Speeds [USRobotics]

USB 3.0 cables can be used with 2.0 devices and ports if the connector types fit (no B Male or B Micro connectors), but the transfer rate will fall back to 2.0.

Source 3: Are USB 3.0 cables different? [UserBenchmark]

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 rewire any existing cabling. USB 3.0 cables have more internal wires, are usually blue, and are noticeably thicker than the old USB 2.0 cables. We figured this out the hard way during the USB flash drive group test.

然後是fixer1234的答案：

You cannot achieve USB 3.0 speeds without a USB 3.0 cable. However, speed is not the only issue.

A USB 2.0 cable will work (at USB 2.0 speeds), for some, but not all, USB 3.0 devices. There are at least three important differences in cable c***truction between the two standards.

Related to Speed:

• USB 3.0 cables have nine internal conductors versus four in USB 2.0 cables.

Four of the nine internal conductors 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 super speed. A good general description can be found here: USB 3.0 [Wikipedia]

• USB 3.0 cables have a limit of three meters versus the USB 2.0 limit of five 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 three meter limit is based on maximum allowable losses using the largest recommended wire size so that the cable is flexible. Specs Document [Zip File – USB.org]

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 900 mA versus 500 mA for USB 2.0 cables.

Additional information on USB 3.0 versus 2.0 can be found here: USB 2.0 vs. USB 3.0 [Diffen]

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