All these USB version names. I used to know what they all meant, but then the USB IF went ahead and renamed them all and made a bunch of versions have the same name and renamed some versions to have the same name as the old name of other versions.
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.
Unfortunately "USB 3.2" is just a version of the standard, which does not give any information about the performance of a USB port or device.
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.
The fact that you had to list all of the versions and speeds at the top of your post is illustrative of what the parent was trying to say. We can all look up what speed is associated with what version, but it’s not exactly a consumer friendly experience.
A few computer manufacturers do the right thing and they mark the speed on the USB ports, removing ambiguities, for example ASUS does this on my NUCs and motherboards.
Unfortunately, there are too many who do not do this, even among the biggest computer vendors.
I can't tell if this is a trick question that has something to do with a quirk of USB running multiple lanes in parallel to get higher speeds.
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.
That's exactly the issue. I'm just pointing out that it's a fantasy to hope for simple numbering of max supported speeds will simplify the current USB mess.
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.
Older Thunderbolt devices were not compatible with USB, so plugging them into an USB Type C port would not work.
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.
USB4/TB4 devices doing (only) PCIe tunneling will absolutely not work on a USB3.2 port, or even on an USB4 port without PCIe support (which you can find on some very recent smartphones I believe. It's spec compliant, PCIe is optional.)
Thats just port speed, charging and other features are all a crapshoot on USB making Thunderbolt the sane version of the "USB-C" family where it requires a set of things (speed, charging wattage)
This is not what’s anti consumer, technical specifications can be confusing, it’s cable companies selling at Best Buy “gold plated” “HD ready” “braided fiber” “other bs” that is anti consumer. If you’re thinking about usb versions, you’re far from the normal consumer
USB 3.2 used to be what we now call USB 3.2 gen 2x2, doesn't it? So it used to be that the version dictated the max speed: 3.0 was 4Gb/s, 3.1 was 10, and 3.2 20, right?
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.
No, they just renamed things when new standards were released (3.1 and 3.2). 20Gbps wasn't possible before 3.2, and it called Gen 2x2 at the time of release.
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
That is technically correct, but "b" has never been an accepted abbreviation for baud (which was Bd) and the naming of the first versions of the PCIe, USB 3 and SATA speeds, which were done by Intel, were obviously in contradiction with the industry standards and intended to confuse the customers.
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.
Yeah, it was a tongue-in-cheek comment. It's a shitshow, and I wish it'd backfire, but it won't. Maybe the EU will come up with some (better) "true labelling" laws, if not I see no chance for this to get better.
(Why the current laws don't cover this, I have no idea. It's technically false advertising.)
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.
The USB A connector stayed the same between USB 1, 2 and 3. Yet most manufacturers voluntary distinguished them by giving USB 1 and 1.1 a white insert in plug and port, USB 2 a black insert and USB 3 a blue one
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 exterior of the USB A connector stayed the same. The number of pins increased when we went from USB 2 to 3. So, even in this case, it’s slightly more complicated. The colors helped because the capabilities were very different between the ports. But when the USB IF increased the number of options (and reduced the size of the connector), different colors became impossible to do.
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.
> Then we decided to just have no markings at all on USB C cables.
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
… and a M1 MacBook will source 5V/3A all day long to a non-PD negotiated sink. Somewhere between the M1 and M3 Apple decided to buy into USB-IF compliance and limit to 500mA.
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)
It doesn't take PD negotiation to get 5v, 3A from a compliant source. A 5.1k resistor or two (quantity depends on placement in the overall circuit) is sufficient.
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.
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 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.
Wow, thanks for sharing this. Like the parent commenter, I have an increasing number of cheap devices like this. I wonder if anyone sells an "enclosed" version of this product. This won't survive 5 minutes in my house, haha.
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.
On AliExpress I found some that were already packaged into neat little professional-looking adapter-sized widgets for about $2.50 each.
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.)
Note: If it just needs 5V power (Like many microcontroller-focused devices), USB C is convenient, because chargers and cables are ubiquitous. And they all (WIth exceptions like the one you mentioned) support 5V DC power.
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.
Ah that's a fun misuse of USB ports. The companies will often even dodge issues with the USB-IF by labeling the ports as Type C and letting the customer's mind fill in the word USB.
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).
I hate barrel jacks, it seems that every single time I encounter one it's different from any adaptor I have. Size, voltage, and polarity can all differ. People got sick of having 10 differnet power adatpters to charge stuff. Hence the demand for "single connector" which seems to have converged on the USB-C form factor.
Right, but if it's not actually USB-C, at best you're looking at the device not working when plugged into a proper USB-C power supply. At worst you're facing fried electronics.
Agreed that would be like wiring a standard North American household wall outlet with 240VAC. Technically possible, but will probably fry anything not expecting it.
I came across a group of racks in the IT room in a (US) factory once that had 208v on their standard NEMA 5-15R sockets.
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.
Have run into that exact thing also, not that the sockets were 5-15R but IEC C13 in a rack CDU. But someone had some adapter pigtails from C14 to a standard NEMA socket, of course that doesn't change the voltage at all. Hilarity ensued.
My aftermarket android auto display uses the type c connector for power input - wired directly to raw vehicle power. It will not run on 5v. It doesn't negotiate pd either. It just expects around 13 volts right on the power pins, and the supplied power cable does exactly that. It's portable too, which means that some poor person plugged their cable into their phone and blew it up.
I repaired device like that a while back - it only took two half-cent resistors and a half-assed soldering job to make it compatible with standard USB-C cables and chargers: https://www.nfriedly.com/techblog/2021-10-10-v90-usb-c/
Yeah, they got cheap. They either got cheap with the BOM, or they got cheap with the QC and never tested it with USB C power sources, or they got cheap with the spec and it's working as-designed.
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.]
USB is just a complete mess. I don't mind so much ports having different capabilities if they are well documented in the specification sheets of the hardware because then at least I can find out what they are capable of, but alas it never seems to be the case. Its very hard to work out whether a port can do Displayport and to what extent/performance or its true power capability or just its real data transfer speed. More often than I like I have just hoped that something works. Anything above 5W charging and 5gbps transfer is optional.
I have an Intel NUC where 10 Gbps devices can run faster when plugged into the 3.1 Gen 2 ports than the Thunderbolt 3 ports under NVMe load, due to the former having dedicated PCIe lanes and the latter sharing the PCH lanes with the M.2 slots, which could be highly relevant if I were doing heavy disk I/O over a 10 Gbit Ethernet adapter.
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?
I miss lightning. Cleanable with a toothpick and some compressed air. The USB-C port on my current iPhone is now compacted with pocket lint and I can't seem to clean it out.
It had a pretty bad flaw: the spring contacts being on the device side, causing wear and tear there.
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.
Going by Fabien Sanglard's cheat sheet (who I trust uncritically) https://fabiensanglard.net/usbcheat/index.html it looks like 3.2 actually is a broader term than expected. Maybe there was some awful attempt at backwards compatibility? Or forwards?
Great site, thanks for the link. But holy heck, that "Also Known As" column is complete chaos. What the heck is wrong with the USB Consortium, do they have brain damage?
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.
Yeah I what I would give to have been a fly on the wall in the room where they decided to roll with such an obviously terrible and stupid naming scheme. Did anyone protest? Did anyone boldly dissent? Or did they all really just sit around and pat themselves on the back?
It allows manufacturers to clear old stocks of cables by rebranding them as latest products.
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.
Probably because with USB 3.2 2x2 they were reviewing too many longer cables that didn't meet the requirements, so they lowered the length so companies didn't submit them only to fail to get certified. It's worth noting that 1.2m is now in the USB4 spec.
To be fair they seem to have taken this often-stated criticism on board. USB 4's naming is more sensible, and they've pushed the simple data speed & power labelling that makes it easier to work out what you need.
I'm not sure I've ever seen that on a product description. But at any rate, USB IF doesn't have any ability to enforce branding guidelines unless the product uses the official USB logo.
In my experience, its just best to stick with Thunderbolt when you want to make sure you are getting the best speed for external devices that require it (external SSD's, Graphics Cards, Network adapters)
Much easier and reliable than navigating the confusing sea of USB standards
While I generally agree, there are still corner cases:
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.
In all this, people now just go to the Apple Store and buy a cable for their Apple device. This confusion benefitted such vendors and now they sell 1$ cable for an absurd amount of profit.
I will say, casual users don't really care. Pretty much any combination of a wall plug and a cable will charge a phone at acceptable speeds, and that's all 99% of people need.
I predict in future when our civilization will advance to higher level, this phenomenon will happen with english words and jargons. e.g. here are versioned and namespaced words. topology.bio.23, topology.math.45 etc.
Welcome to the brave new world we will enter in far future.
It means that if I pick up a random USB cable and plug it into a USB port I have no idea how well it will work or even if it will work at all. It's like the U in USB stands for Unpredictable.
Now I only buy USB cables if they are marked with their speed and wattage. If it’s not marked, I have to assume it carries little power and is glacially slow, which is fine to charge some Bluetooth headphones but is not usable to connect an SSD.
Get a certified cable if it matters to you. If you pick a random cable out of the cable box it’s probably a 2.0 charging only cable that hasn’t been certified by USB IF.
Ultimately the majority of people only use usb cables for charging or 2.0 speeds for their keyboard or mic so this isn’t a problem. And for those who it is a problem, they know which one their high speed cable is.
I use cables that look exactly the same to hook up sound boards, SSD’s, HDD’s, remote KVM switchers, phones, computers, tablets, peripherals of every shape, size, and demand. One livestream station (we have multiple) has literally 10-15 of these cables hooked up and the demands vary across devices. It is incredibly important that I know what I am using and what it is hooked up to. I can’t have random things flashing off and on or under-powered when I’m running live streams at work. I can’t be constantly swapping cables because data transfers are suddenly 1/10th what I expected.
This is not some minor inconvenience. It is a serious problem that creates completely avoidable hurdles. We have to label everything so meticulously and anytime somebody asks to borrow/use any usb-c cables from my department, we have to be incredibly particular about what we hand off.
HDMI? Whatever grab it from the drawer. USB-C? I need to assemble a committee and find out your use case, as well as when we’ll get it back. It’s absolutely ridiculous.
The only consistent solution is to massively over spec and spend 10x on cables you don’t need.
All I know is that I pick up some cables they work for some things and then I try to use them for other things and they don't work.
Isn't the whole point of the USB standard to make it so you don't have to be a super nerd to plug stuff together? People just want to transfer data from their phone or camera to a laptop without navigating spec sheets.
Would you recognize the difference between usb 3.2 and usb 2.0? Cables also play into the standard and the reality of our modern lives is that we all accumulate random cables as a matter of course of life. Sometimes things get mixed up and if you didn’t label the cable in some way when you acquired it, there is no way to easily test it without a lot of hassle and headache.
For me, it makes a difference much later on after buying some computer. I see a usb/c port and think I can plug anything into it that fits and it just works.
When it doesn't, it will take hours/days to figure out why and if it comes down to a cable incompatibility, I would have already made the mistake of not knowing what I was buying.
Because this is an article about network adapters where someone again rants over USB markings which won't make a difference on the tested adapters if you exchange them.
It's just ranting for ranting sake, not even related to topic at hand.
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.