What does "This port is for data transfer only" mean in relation to USB-C graphics output?

There’s no such thing as a USB 3.1 data-only port that is compliant with all the standards. However, some manufacturers use cheaper USB ports, by only implementing some of these standards.

One of the most common omissions is that of power charging, since data transfer alone needs less power than does charging. One can see this more clearly by examining USB Type-C cables, which by definition should offer up to 10Gbps data rates and 100 watts of power. However, many cheap USB cables designed for data transfer can only supply about 10Wh of power, insufficient for many devices such as the Apple MacBook or Google Chromebook Pixel 2 that charge at 29Wh.

USB 3.0 ports can only be used for data transfer. Users of USB 3.0 devices devices can purchase adapters allowing them to use the newer USB 3.1 Gen 1, but again, for data transfer only. My opinion is that the specifications of the Asus ZenBook mean just that: The USB 3.1 port is only a frontal adapter to older (and cheaper) USB 3.0 hardware.

A full implementation of the USB 3.1 standard means the USB port can do a lot of things: Data transfer, video and charging. The Thunderbolt 3 specification piggybacks on USB 3.1 ports, meaning that manufacturers like Apple can make computers with USB 3.1 ports that are also Thunderbolt ports.

"USB 3.1 Gen 1 (data transfer only)" means therefore the USB 3.1 protocol, but at half the speed and without video, charging, or Thunderbolt capabilities. As most USB 3.X devices can negotiate capabilities with the port or the cable, most USB 3.1 devices using data transfer will still function, but at lower levels of performance.

harrymc

Posted 2018-11-26T00:58:21.493

Reputation: 306 093

"USB 3.0 ports can only be used for data transfer." I think you mean USB-A. The Lenovo Yoga 730 advertises "2 x USB 3.0 Type-C (Thunderbolt 3, 1 x power delivery)" for example. https://www.lenovo.com/au/en/laptops/yoga/yoga-700-series/Yoga-730-13-/p/88YG7000964 So the port features appear to be entirely related to the port type (and implementation) rather than the USB protocol version as in @Keltari's answer.

– tu-Reinstate Monica-dor duh – 2018-12-01T21:55:25.987

USB-C was created at the same time as USB 3.1, so I think that "USB 3.0 Type-C" is a misnomer for "USB 3.1 Type-C". There seem to be all sorts of hybrids around, probably dating from times that standards were proposed but not yet finalized, thrown to the market by manufacturers jumping the gun to be the first. The Asus seems to have one of these hybrids: A USB 3.1 that is more like USB 3.0 underneath. Your link above seems to be another, an almost-USB 3.1 from before the standard was published. – harrymc – 2018-12-01T22:16:53.240

Yes, they were created at the same time but they don't appear to be linked. Wikipedia, for example, lists alternate modes under USB-C and not USB3.1. https://en.m.wikipedia.org/wiki/USB-C#Alternate_Mode Conversely, the specification for USB3.1 doesn't require a USB-C port (e.g. "Type-A USB3.1 port" appears alot in the wild) so they appear to be independent specifications which can be mixed and matched. Do you have a reference that says the USB3.1 specification requires a USB-C port?

– tu-Reinstate Monica-dor duh – 2018-12-01T22:25:28.223

I don't think that one requires the other, except in the eyes of the marketing department. It makes marketing sense to label a port as the up and coming USB 3.1, even if it's not really, especially since you will never know the difference except for those missing capabilities. USB-C is also a useful addition to the hype. As they both came out at the same time, both became a marketing necessity. Marketing demands may drive hardware development, although we would have liked it otherwise. – harrymc – 2018-12-02T08:08:43.747

If one doesn't require the other then there's no link between USBx.y Gen z and (port type) USB-x, so it's true that USB3.0 can only be used for data transfer because the statement would be true of all USB versions. It's the port type that dictates the modes available and not the protocol version. What's not true is that "USB 3.0 port can only be used for data transfer" because, from the way I read it and from the specifications I've seen, any manufacturer could implement Thunderbolt, HDMI, and/or power charging on a USB-C port and then use the version 3.0 protocol for data transfer. – tu-Reinstate Monica-dor duh – 2018-12-02T22:57:31.730

USB-C/Type-C is required to achieve USB 3.1 speeds, because it has the additional pins required for the protocol. True, the two are not dependent, but one without the other is crippled/useless. You may stick a Type-C port on top of USB 3.0, and you would get exactly what you have on the Asus. Without both, Thunderbolt is somewhat useless and cannot achieve the required speeds, so I don't think anyone ever bothered to implement it over USB 3.0, even if theoretically possible (who knows), as it's rather pointless. – harrymc – 2018-12-03T07:27:12.267

Ah, I see. USB-C can carry HDMI and/or DisplayPort, so what they mean is they've only connected it to the USB hub, just like their other USB3.1 ports. So the connector is just a connection advantage and not a functional one. They may as well have provided 3 type-A ports as it really doesn't do anything more. – tu-Reinstate Monica-dor duh – 2018-11-29T01:45:30.423

@tudor you are correct – Keltari – 2018-11-29T01:52:38.800

What does "This port is for data transfer only" mean in relation to USB-C graphics output?

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