I have absolutely no idea what anyone means when they say USB 3.2 gen 2x2. I used to know what USB 3.2 meant but it's certainly not that.
USB 5 Gb/s = USB 3.2 gen 1, available on Type A or Type C connectors (or on devices on a special extended micro B connector)
USB 10 Gb/s = USB 3.2 gen 2, available on Type A or Type C connectors
USB 20 Gb/s = USB 3.2 gen 2x2, available only on Type C connectors
Moreover, "5 Gb/s" is a marketing lie. The so-called USB of 5 Gb/s has a speed of 4 Gb/s (the same as PCIe 2.0). On the other hand, 10 Gb/s and 20 Gb/s, have the claimed speeds, so USB of 10 Gb/s is 2.5 times faster than USB of 5 Gb/s, not 2 times faster.
10 Gb/s USB and Ethernet have truly the same speed, but the USB overhead is somewhat higher, leading to a somewhat lower speed. However, the speed shown in TFA, not much higher than 7 Gb/s seems too low, and it may be caused by the Windows drivers. It is possible that on other operating systems, e.g. Linux, one can get a higher transfer speed.
Unfortunately, there are too many who do not do this, even among the biggest computer vendors.
Unfortunately it's not true.
Quiz: what happens when a device capable of 20Gbps is plugged into a port marked as 40Gbps?
Because if not then it's the same as any specification for connecting devices that allows for multiple speeds. It runs at the lowest of the max speeds supported of everything in the chain.
It will not.
Consumers would expect plugging a 20Gbps device into a 40Gbps port should result in 20Gbps negotiated speed. In reality it will mostly likely end up at 10Gbps (or less) because of the mess.
Newer Thunderbolt/USB 4 devices do not have any technical reason for preventing them to work as USB 3.2 2x2, i.e. to work at 20 Gb/s when plugged into a 20 Gb/s host port, and vice-versa for 20 Gb/s devices plugged into a USB 4/Thunderbolt host port, because both Thunderbolt and 20 Gb/s USB need the same wires in the cable and connector.
I do not know if all USB 4 controllers also work at 20 Gb/s (USB 3.2 2x2), but if they do not work that should be considered a bug.
It's not a lie, the b just stands for baud not bit ;-)
Previously to these standards promoted by Intel, the 1 Gb/s Ethernet used the same encoding and it was rightly called by everybody "1 Gb/s", not "1.25 Gb/s", because the gross bit rate has absolutely no importance for the users of a communication standard.
Only Intel invented this marketing trick, calling PCIe 1.0 and 2.0 as 2.5 and 5 Gb/s, instead of 2 and 4 Gb/s, and similarly for USB and SATA, where e.g. SATA 3 is called 6 Gb/s, but its speed is 4.8 Gb/s.
To be fair, what Intel did was not unusual, because in the computing industry there has been a long tradition of using fake numbers in marketing for various things, like scanner or video camera resolution ("digital" zoom, "interpolated" resolution), magnetic tape capacity ("compressed" capacity), and many others.
(Why the current laws don't cover this, I have no idea. It's technically false advertising.)
But then they decided to memory hole that and now USB 3.0 and USB 3.1 are also USB 3.2 and USB 3.2 is called "generation 2x2", whatever that is supposed to mean
It makes no sense anymore. It used to be quite simple.
5 and 10 Gbps were renamed, though.
5 Gbps first was USB 3.0, then 3.1 Gen 1, then 3.2 Gen 1.
10 Gbps first was 3.1 Gen 2, then 3.2 Gen 2x1.
3.2 Gen 1x2 is also 10 Gbps, but physically different
The lack of clarity is in keeping with the USB C connector itself, which may supply or accept power at various rates or not at all, may be fast or slow, may provide or accept video or not, and may even provide an interpretation of PCI Express but probably doesn't.
It probably looks the same no matter what, and the cable selected to use probably also won't be very forthcoming with its capabilities either.
(Be sure to drink your Ovaltine.)
This was neither standarized nor enforced, yet it worked remarkably well in the real world
Then we decided to just have no markings at all on USB C cables. On the ports at least we occasionally get little thunderbolt or power symbols
The problem is that there are too many uses for one connector. But this is wha we wanted - a reduced number of standardized connector/power options.
Some USB C cables identify their capabilities visually or electronically. All USB C cables could do this.
> But this is wha we wanted - a reduced number of standardized connector/power options.
We meant who?
I'm shocked the LTT TrueSpec cables are the first I'm aware of to so such a small and basic thing. I have so many USB C cables and no idea which are power only, USB 2 only, or what. Such a mess
It gets even worse.
I now have two cheap Chinese gadgets (a checki printer and a tire inflater) that have USB-C ports for charging, but will only charge with the wire that came with the gadget. The other end of which is an old-style USB plug.
It seems that USB-C sockets are cheap enough parts to use them for everything, even if the manufacturer isn't going to put any actual USB circuitry behind them.
Edit: Three. I forgot about my wife's illuminated makeup mirror.
Very annoying though! The devices are just missing a couple resistors which is probably less than a cent on the BOM.
A quick google I found one but they're $17 each (!) and it's from a site I've never heard of and can't vouch for, so not bothering to link it here.
I'm really surprised there aren't a number of these all over Amazon. Or if there are, they're using different keywords to describe them, so I can't find them.
I'd link them here, but I have a US perspective on things and it wasn't clear to me how this listing would be delivered. And delivery method is important to me, here.
If with AliExpress Choice shipping, then that'd be fine: They'd show up on a doorstep in Anytown, USA for a few dollars each.
But if they'd be delivered using Approximately Any Other Method, then: Surprise! Your widget valued at less than $2.50 now costs you $80 to receive!
I don't want to encourage anyone to be surprised like that.
(I have no doubt that an enterprising person could negotiate a very good price on 1,000 of these widgets and sell them on Amazon if they were motivated to do so.)
I wish these devices would just use barrel jacks, labeled with the voltage and polarity. But these manufacturers know that the USB-C port weighs into buying decisions (and they know that most people have zero clue about the difference between a physical port and the electrical/protocol specs).
Their global-market IT stuff didn't care at all. But some of the US-market audio stuff I was integrating came with old-school linear power supplies, and those items cared a great deal.
Bonus: YOu can enable USB 2.0 data transfer as well for firmware updates, computer interfaces etc.
So: Cheap/ubiquitous part, everyone has cables + AC adapters to their local plug: I think it's a great default power connector.
It just takes a couple of insignificant resistors and a USB C socket that brings out CC1 and CC2 to pads on the board to do it right. I wrote about how that works in a sister comment if you want to read more.
But those devices will charge/work just fine with any bog-standard USB A to USB C cable, alongside any decent power brick with USB A outputs. It doesn't have to be the exact cables they came with.
It's annoying in the "you cheap bastards" sort of way, but regular A to C cables will work.
(If it's really important to you, then it can be possible to hack in a couple of 5.1k resistors inside the cheap-bastard devices and make them work with regular USB C power bricks and regular USB C to C cables. The resistors will tell the source to provide 5v at up to 3A. All compliant USB C cables are required to safely pass 3A.
The mod can range from very easy, to somewhat problematic, to "fuck this, I quit". In reality, there might already be pads on the board to connect CC1 and CC2 to ground; just solder in the resistors. Or, the pins are probably brought out at the connector itself, so it can be bodged with some extra wire.
But reality is a cruel mistress and not all available PCB-mounted USB C connectors expose CC1 and CC2 at all, although in a sane and pure world absolutely all of them should.)
[tl;dr, just keep an A to C cable with the devices, always have USB A where they get used, and forget about it. The next round of cheap stuff will be better, worse, or the same, and that's a future problem.]
Has lead to some very embarrassing “works on my computer” situations on prototype boards shared with my EE colleagues (I’m a software guy who dabbles in hardware when I need to)
This may be a matter of semantics, but I can't bring myself to call a resistor a negotiator. They only do one thing and they're very resistant to other options. :)
With nothing connected to the CC line(s) at all, then there should be no output voltage on Vcc. It shouldn't be 5v @ 3a, or 500mA, or anything else -- it should be ~exactly 0v, and therefore also 0a.
A resistor or two tells the power source what we want. Without it (or some, you know, actual PD negotiations), we get nothing.
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A careful reader will note the repeated quantity distinction. Let me explain that.
Every USB C socket has both CC1 and CC2 pins. They're on opposite side of the connector and get used for sorting out PD, and for detecting the cable's connector orientation (if/when that matters).
But a cromulent USB C to USB C cable can have just 1 CC wire, and that's OK. It works; it isn't even wrong. To get such a cable to coax 5v from a 5v/3a source and get power for a prototype widget on Gilligan's Island, with the cable already cut in half to get at the wires inside: Wire up power and ground to your prototype. And put a 5.1k resistor between that single CC wire and ground. Voila: We've requested 5v at up to 3a.
Or: If we're being a bit more proper and snooty and want to do it The Right Way, and we actually have a USB C jack to prototype with, then that more-ideally takes two 5.1k resistors; one to pull CC1 to ground, and another to pull CC2 to ground. This does the same thing, but it does it on the connector side of things instead of the daunting no-mans-land of wires. Only one of these resistors will ever be used at one time.
Or: If we have a USB C jack and can only scrounge up one 5.1k resistor (maybe we only have a single #2 pencil to whittle down to 5.1k of resistance), or we're being particularly lazy, then that's OK too. Pick CC1 or CC2 and put 5.1k between there and ground. It will work with the cable plugged in one way, and it won't work with the cable flipped 180 degrees. That can be enough to get a thing done for the moment or whatever. (There's no solution that is as permanent as a temporary one.)
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These are some of the things I learned when I was in the field and needed a 5v, >2.5a power supply to replace one that had died. I said to myself, "Self, just go over to Wal-Mart and get a 3a USB C power brick that comes with a cable, cut and splice that cable to fit the widget that needs power, and call it done. If it dies in the future, replacing it will be intuitive and fast."
So dumb ol' me went to Wal-Mart and bought exactly that, and I quite confidently set forth with the splicing.
This did not work. At all.
And that was a harsh rabbit hole to dive into, but it was ultimately fine. After I got back that evening I soldered a 5.1k resistor (of 1206 SMD form) mid-span between the CC wire and ground, and finished the adapter-cable quite neatly with some adhesive-lined shrink tubing.
Doing it this way got the customer's gear working faster than ordering the "right" parts and waiting for them show up would have, and it still works. That's all been a few years ago now; I consider it to be as permanent as anything ever really is.
You have to go out of your way to make Apple's Lightning connector look sensible, but somehow the USB consortium has managed to do it.
USB-C moved those to the much cheaper to replace cable. The little strip in the middle makes cleaning a bit harder but does provide for more longevity. It's s necessary evil in order to have the spring contacts on the plug side as well as not having them exposed to touch.
I think the plug side of USB is pretty well designed. The problem is more with the electrical and signalling side and the marketing of the different versions.
This is more than a mild annoyance in the case of faster Thunderbolt devices like eGPUs, especially since, in addition to the 2 PCIe lanes dedicated to the USB ports and a third dedicated to an SD card slot, an additional five lanes are unused.
IIRC there was a reason at one point that Intel insisted on connecting Thunderbolt controllers through the PCH, but I don't understand why they didn't at least use four lanes for one of the M.2 slots. Sure, they may have had to move the SD card slot due to configuration limitations, but in what world is SD card performance more important than NVMe performance?
Also, according to that table, "USB4 Gen 2×2" is a downgrade on "USB 3.2 Gen 2x2", since the cable length is 0.8m instead of 1m for the same speeds. Which is uhh unexpected.
USB 1+2/3/4 are basically unrelated standards under the same USB umbrella. USB4 especially is just Thunderbolt/PCIe x4 with features. If Betamax was branded as "VHS 2.0" instead of being a separate standard it would have been felt similar to the USB4 situation.
Rather than some absurd version number it’s now just “USB 20 Gbits”
Much easier and reliable than navigating the confusing sea of USB standards
As I mentioned above, a Thunderbolt port can end up with less dedicated bandwidth than a 10 Gbps USB port due to PCIe lane configuration.
Thunderbolt 3 only provides 22 Gbps PCIe bandwidth even if only a single device is connected.
Apple's TB2-to-TB3 adapter will connect any TB2 device to any TB3 host, and any TB3 (not USB) device to any TB2 host unless it's bus powered, in which case you need to daisy-chain a second TB3 device with two ports to supply power.
While Thunderbolt 4 and USB 4 PCIe are largely interchangeable, and while Thunderbolt 4 devices are backwards-compatible with Thunderbolt 3 hosts, USB 4 PCIe devices are not required to support Thunderbolt 3 hosts.
Welcome to the brave new world we will enter in far future.