Tuesday, July 16, 2019

How Many Kinds of USB-C to USB-C Cables Are There?

Benson Leung (via Hacker News):

We have a matrix of 2 x 3, with 2 current rating levels (3A max current, or 5A max current), and 3 data speeds (480mbps, 5gbps, 10gpbs).

Adding a bit more detail, cables 3-6, in fact, have 10 more wires that connect end-to-end compared to the USB 2.0 ones in order to handle SuperSpeed data rates. Cables 3-6 are called “Full-Featured Type-C Cables” in the spec, and the extra wires are actually required for more than just faster data speeds.

“Full-Featured Type-C Cables” are required for the most common USB-C Alternate Mode used on PCs and many phones today, VESA DisplayPort Alternate Mode. VESA DP Alt mode requires most of the 10 extra wires present in a Full-Featured USB-C cable.

Alexis Gallagher:

Inconvenient but not crazy. I’d say the design failure here is the absence of a system of clear graphic symbols to convey this.

Jonathan Wight:

Assuming no one has invented a USB-C hub yet? (USB-C <-> USB-C).

Still just a bunch of USB-3 hubs or overpriced “docking stations”…

See also: USB-C Charger Roundup.


5 Comments RSS · Twitter

"The USB spec also cannot simply mandate that all USB-C cables have the maximum number of wires all the time because that would vastly increase BOM cost for cases where the cable is just used for charging primarily."

Uh... why not? That's what they should do -- it would solve the entire problem! We're talking about the difference of probably 20 cents (at MOST) of materials at the manufacturing level for a standard 1 meter cable. I mean isn't one of the promises of USB-C is that you don't have to think about it? That you can use either end of the cable, you can plug it in any orientation, and you can use any cable? Otherwise if I have to think "Oh, this cable is just for charging, but that one over there can do data"... what the hell is the point?!? Might as well stick with USB-A where at least I can tell by looking at the cable what it can do.

USB-C is starting to seem like a completely ridiculous non-solution to the problems that it originally set out to solve.

Ghost Quartz

@Ben G
The problem isn’t the additional wires, it’s that higher speed USB-C cables have shorter maximum lengths [1]:
- 4m for USB 2.0
- 2m for USB 3.1 Gen 1
- 1m for USB 3.1 Gen 2

Rather than compromise on bandwidth or maximum length, they opted to compromise on usability by allowing both kinds of cables. Alternatively, they could’ve specified that USB-C cables of all lengths must support 10Gbps, but then you’d end up in the situation we have with Thunderbolt, where long cables are absurdly expensive because they’re either active copper or optical. (This is why every Thunderbolt 3 dock comes with a ~0.5m cable, by the way.)

[1] https://hackernoon.com/usb-c-cheat-sheet-db85d6627401

Interesting, thanks for the correction!

@Ben G,

>20 cents (at MOST)

That is the problem with people aren't familiar with commodity trading. Imagine your profits for each cable is only 10 cents, cutting 20 cents from BOM for a specific use would instantly increase your profits by 20 cents, or 200% increase. On a consumer level this isn't obvious because a large potion of the price are in Retail, Staff, Rent, Logistic etc... on a OEM level those cents are everything. Even 1 cents saving represent a possible 10% increase in profits.

If only we had some sort of numbering or lettering scheme which could differentiate cables... NAH

(this is a big reason why I’ve always disliked USB-C)

Leave a Comment