Nope... it's even more complicated. Up to "3.2 Gen 2x1" they have 8 wires, but "3.2 Gen2x2" has 12 wires. There's two pairs of RX and TX each, i.e. RX1- RX1+ RX2- RX2+ TX1- TX1+ TX2- TX2+ D- D+ PWR GND = 12.
And... that's still not correct: USB-C to USB-C cables have an additional CC line which carries the Type-C extra negotiation (e.g. alt mode switch, power levels.)
And just to fuck users over even more, there is a difference between a 13-pin full-function "USB 3.2 Gen2x2" cable and a 13-pin full-function Thunderbolt cable: the Thunderbolt cable reports an extra "vendor descriptor" on the Type-C negotiation channel, indicating support for TB. The cables are otherwise physically identical, but these extra bits come with a ~$15 markdown.
(Oh and the PWR/GND lines can be 3A or 5A, but at this point...)
The article is, however, correct in its conclusion: a "Thunderbolt" cable will always work for all USB standards. The only free variable on a TB cable is whether it does 3A or 5A for power.
USB-C cables either have all 4 superspeed lanes wired up, or none of them. Which is why USB-C docks with video worked (2 lanes for USB, 2 lanes for DisplayPort) and why 2x2 isn't supposed to require new cables.
Thunderbolt still works at 20gbps over "normal" superspeed USB-C cables; the markup you're paying is generally for cables rated for 40gbps.
Your first paragraph is technically right but in actual reality cables with only 2 superspeed lanes exist. Also, the article (and comment) aren't solely about Type C; USB3 cables going to good ol' A/B will only have 2 superspeed lanes.
Your second paragraph is half-wrong. Thunderbolt cables must have an e-marker: refer to https://www.usb.org/sites/default/files/USB%20Type-C%20Spec%... Figure F-1 ("SOP'"). If the cable has an e-marker but doesn't have the Thunderbolt ID, you get passive Gen2. However, the problem is that USB3 TypeC-C cables aren't required to have an e-marker at all... in which case you drop out at the very first fork in the flow diagram.
This also leads to the funny situation that any 5A USB3 cable should work for Thunderbolt (because 5A requires the e-marker), while 3A cables may or may not work. I mean, of course the power rating makes complete sense to determine TB3 capability, right? :D
> The article is, however, correct in its conclusion: a "Thunderbolt" cable will always work for all USB standards.
Aren't active (i.e. >50cm) Thunderbolt 3 cables incompatible with USB 3 speeds due to having some active amplifier incompatible with the USB line signals?
Teeeeeeechnically I think yes, however in practice active cables are extremely rare (they start beyond 2m, not 50cm EDIT: incorrect, sorry!) and the redriver might even work for USB3 even if it's not specified. There isn't really all that much difference on the barebones electrical level; the most significant factor is the symbol rate, which is in the same range.
(Not sure if the Type-C negotiation will prevent them from working; it might.)
Ed.: after a quick check, active cables seem to crop up at 40G && >= 1m. 40G 2m cables seem to all be active, at 1m it's either. Couldn't find any "20G" active cables.
From what I've read, the redriver does break USB 3 connectivity [1], but it might also be the marker chip not explicitly indicating USB3 support.
And I think the maximum length for passive Thunderbolt 3 40 Gbit/s cables is indeed 50cm [2]! 50-200cm would be 20 Gbit/s only; anything above always requires active cables.
You're probably right, I can't check the TB spec but from what I see in shops I'm gonna say those "passive 1m 40G" cables are manufacturers breaking the spec. I'm also seeing "20G" cables that claim to only do 5G USB3, which is concerning & confusing me quite a bit...
FWIW my confidence level on "would an active TB3 cable work for USB3 if it had the proper bits set" is somewhere along 66% to 75%; this is based on the SERDES in some (most?) TB3 host silicon being able to switch to USB3 to "downgrade" a port... meaning the electrical level can't be all that different... but I haven't dug into this.
While we're at it, I forgot the 2 SBU pins too, so that's 2 extra wires for TypeC-TypeC cables... neither USB nor TB uses them; native DisplayPort does (not including DP over TB)
About a year ago I switched to an iPhone after being a longtime (~10 years) Android user. Last night I was at the grocery store and impulse-bought a Lightning charging cable to carry in my hiking backpack. No way I would ever have trusted a checkout-lane USB cable, but Apple's tighter controls give me a greater assurance that the cable will work well and not damage things.
OP never said if he bought a legitimate Apple cable or a third party one. I don’t think I’ve ever seen genuine cables in these kinds of shops even when I travel to Europe but that could still be a locale thing.
If that's a third party cable, you did take some risk on your iPhone. Third party cables and chargers (made with cheap components and poor design) may not function as expected or can be harmful to the device and to you (or people around you), at worst.
Apple keeps a pretty tight lid on MFI though, right? As long as the box has MFI on it, it's probably legit, unless you're really looking on the grey market, I think.
I really doubt Apple is able to police the supply chain that leads to the check out counter of a convenience or even grocery store. There's no way to know that the MFI logo on the box is legit or not.
I don’t know how successful they are, but the whole point of MFI is to give Apple the ability to send the USG after you if you use the logo without permission. I mean, there are also fake Rolexes and fake Gucci bags, but those are the exception because the companies mostly do a good job of suing the violators.
Nope... it's even more complicated. Up to "3.2 Gen 2x1" they have 8 wires, but "3.2 Gen2x2" has 12 wires. There's two pairs of RX and TX each, i.e. RX1- RX1+ RX2- RX2+ TX1- TX1+ TX2- TX2+ D- D+ PWR GND = 12.
And... that's still not correct: USB-C to USB-C cables have an additional CC line which carries the Type-C extra negotiation (e.g. alt mode switch, power levels.)
And just to fuck users over even more, there is a difference between a 13-pin full-function "USB 3.2 Gen2x2" cable and a 13-pin full-function Thunderbolt cable: the Thunderbolt cable reports an extra "vendor descriptor" on the Type-C negotiation channel, indicating support for TB. The cables are otherwise physically identical, but these extra bits come with a ~$15 markdown.
(Oh and the PWR/GND lines can be 3A or 5A, but at this point...)
The article is, however, correct in its conclusion: a "Thunderbolt" cable will always work for all USB standards. The only free variable on a TB cable is whether it does 3A or 5A for power.