I think that maybe having two similar lightning bolt symbols that mean different things wasn’t the best design decision that the USB guys could have made.
The ‘Thunderbolt’ symbol is Intel’s proprietary technology. Apple and Intel made it. First apple registered Thunderbolt as a trademark but later they transferred it to Intel. The lightning bolt icon which supports fast charging phones or other devices when connected to the laptop is different and developed by the USB guys.
Everything defined in the Thunderbolt 3 spec was incorporated into the USB 4 spec, so Thunderbolt 3 and USB 4 should be basically identical. In reality the two standards are enforced by different certification bodies, so some hardware manufacturers can’t really market their compliance with one or the other standard until they get that certification. Framework’s laptops dealt with that for a while, where they represented that their ports supported certain specs that were basically identical to the USB 4 spec or even the Thunderbolt 4 spec, but couldn’t say so until after units had already been shipping.
One should note that though Thunderbolt over USB-C offers the same speed and connectivity as a native thunderbolt cable, the native cable can be 40m long whereas the USB-C implementation is max 2m
The USB-C standard and particularly the USB PD (power delivery) is so complex it almost feels comical.
The PD standard document (freely available on usb.org) is over 800 pages long and features a lengthy part about the role of the cable alone which is mostly hidden from the user. Here’s a short video about this issue: www.youtube.com/watch?v=6bZ0y9G-4Pc
It gets even better, each function of the port also needs proper support from the cable. Often cables do not support the full spec of usb to cut costs.
While the symbols in the post are often put on computers, for usb cables this is seldom done (only a few brands do).
Source: had to find a cable that supports both DP and PD to connect a portable external monitor after I lost the original cable. (1/9 cables worked)
Luckily, all new PC seem to choose Thunderbolt over only alt mode, which makes stuff more easy, since they have the flash on the cable (but are also more extensive, I gear
That sounds like a dedicated charging cable. So yeah, they will (if at all) only transfer data slowly and not support any extras features like displayport.
No USB cable has “gigabit speed”. It probably has 480 Mbps (USB 2.0 standard).
Maybe he meant a 5 Gbps Gen1 cable. That would be “gigabit speed” but still rather slow by today’s standards and won’t support DP. They are pretty cheap these days, so wouldn’t be suprising to see left over stocks being sold as charging cables.
Didn’t really think about that one but you’re right damn… (Looked it up, and it depends on the bit depth etc, but it’s around 3.2Gbps for the display settings if I’m correct)… So that explains a lot
Gigabit is capable of like 720p@30Hz which it probably should be able to fall back on, but I understand why they wouldn’t do that haha. 1080p@15Hz is also possible :)
USB-C video is usually DisplayPort Alt Mode, which uses a completely different data rate and protocol from USB.
Even using old 2016 hardware, a computer and USB-C cable that both only support 5 Gbps USB (such as USB 3.1 Gen 1) can often easily transmit an uncompressed 4K 60Hz video stream over that cable, using about 15.7Gbps of DisplayPort 1.2 bandwidth. Could go far higher than that with DP 2.0.
Some less common video-over-USB devices/docks use DisplayLink instead, which is indeed contained within USB packets and bound by the USB data rate, but it uses lossy compression so those uncompressed numbers aren’t directly comparable.
For that portable monitor, you should just need a cable with USB-C plugs on both ends which supports USB 3.0+ (could be branded as SuperSpeed, 5Gbps, etc). Nothing more complicated than that.
The baseline for a cable with USB-C on both ends should be PD up to 60W (3A) and data transfers at USB 2.0 (480Mbps) speeds.
Most cables stick with that baseline because it’s enough to charge phones and most people won’t use USB-C cables for anything else. Omitting the extra capabilities lets cables be not only cheaper but also longer and thinner.
DisplayPort support uses the same extra data pins that are needed for USB 3.0 data transfers, so in terms of cable support they should be equivalent. There also exist higher-power cables rated for 100W or 240W but there’s no way a portable monitor would need that.
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