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USB Cheat Sheet (2022)

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Re: USB Cheat Sheet (2022)

#81

Post by adrian_b »

crote wrote: post #71
Liftyee wrote: post #63

Earlier quoted context omitted.

The wires count seems to be the number of conductors in the cable (i.e. the number of wires you'll find if you cut a cable in half, including ground and power). It's true that the actual data is sent over a lower number of diffpairs. I suspect the shield is not included in the number of wires, since all USB cables have a shield (not sure if usb 3.0 has an extra return ground wire for high speed).

It still would't be right. Full-featured USB-C has 8x superspeed (tx1p, tx1n, rx1p, rx1n, tx2p, tx2n, rx2p, rx2n), 2x high-speed (dp, dn), 2x power (vbus, gnd), 2x SBU, 1x CC. That's 15 wires.

A full-featured USB-C connector has 24 pins, as shown in a diagram in the parent article.

The "12-wire" count of the parent article refers only to the main wires, i.e. the 4 USB 2.0 wires + 4 differential pairs for USB 3 or 4.

Similarly, the "8-wire" count for Type A connectors refers only to the main wires, i.e. 4 USB 2.0 wires + 2 differential pairs for USB 3.

Re: USB Cheat Sheet (2022)

#82

Post by QuantumNomad_ »

phatskat wrote: post #56
QuantumNomad_ wrote: post #49

Earlier quoted context omitted.

I have a USB hub that I bought recently, that has very nice markings on it that are almost like you say :) I connects via USB4 to the host, and has the following markings on its ports: - Power in/USB 10Gbps - USB 10Gbps - USB 10Gbps - 8K HDMI Pretty happy with this one so far.

I got a jCreate5 hub at clearance from an Office Max (rip) and the ports are labeled just like this, no futzing on which port is the PD

Maybe we even have the same one :)

Mine's this one:

j5create USB4 8K Slim Hub - 8K60/4K144 HDMI, 1 x USB-C 10Gbps with PD charging, 1 x USB-C 10Gbps, 2 x USB-A 10Gbps | Compatible with MacBook, Windows Laptops (JCH453)

https://www.amazon.co.uk/dp/B0C8NDXH8S

I bought it because unlike many other USB hubs, the host connection is USB4 / Thunderbolt 4, instead of just USB3 for the host connection.

> Ultimate Connectivity: JCH453 combines the latest USB4 controller with Thunderbolt 4 and USB compatibility, ensuring seamless connectivity with various devices. Experience the power of multiple ports in one hub.

Manufacturer product page:

https://info.j5create.com/products/jch453

> A USB4® multi-port hub incorporates the latest USB4® controller offering compatibility with Thunderbolt™ 4 and older USB™ specifications.

> With up to 40Gbps of throughput, dynamic data, and display bandwidth allocation for efficient display data flow, you can easily create a high-definition monitor setup.

Re: USB Cheat Sheet (2022)

#83

Post by fabiensanglard »

DHowett wrote: post #10

Excellent article. If I could offer one correction, it would be that SBU (as specified by the USB 3.0 Promoter Group[1]) means "Sideband Use" rather than "Secondary Bus". On some devices, it is used to carry UART; on others, audio. [1]: https://www.usb.org/sites/default/files/USB%20Type-C%20Spec%... (pdf)

Thank you for taking the time to report the issue. It has now been addressed.

Re: USB Cheat Sheet (2022)

#84

Post by analog31 »

nawi wrote: post #73

this is great, does usb cable has some limitation? can i take any length? i saw you measure 4m any advices longer cable?

I've tried longer cables on the slower USB's. My experience is that it can be touch and go depending on the peripheral. As I understand it, cable length is limited by the round-trip time between the host and the peripheral.

Where I've had good and bad "luck" with USB cabling is video cameras, which require a fairly high bandwidth data stream.

Re: USB Cheat Sheet (2022)

#85

Post by joveian »

adrian_b wrote: post #80
Neywiny wrote: post #68

Earlier quoted context omitted.

This goes back to another point I've historically made which is that except for storage devices, pretty much nothing supports those speeds. I think there are some USB adapters that don't use alt mode and that can have some advantages on some hosts but usually that's a disadvantage. USB interface chips are, as far as I've seen, a Cypress/Infineon FX3 or a bit more rare FTDI FT600/FT601. I even talked with the FTDI guy…

Besides storage devices, i.e. external SSDs, which are very frequently used and they need a USB port as fast as possible, the other frequent application that needs the fastest USB ports is the use of USB Ethernet interfaces.

Also eGPU. I have a tiny NUC-size system with decent internal GPU and a (physically much larger) game system with a slower CPU that idles at only a bit under twice the maximum power of the NUC. It would be handy to be able to just plug in an eGPU when needed. The power and cooling requirements of fancy GPUs are so much higher than that of CPUs that large cases designed around the CPU don't make much sense. Even the pysical stability of a large GPU in an ATX style case is not ideal.

Re: USB Cheat Sheet (2022)

#86

Post by mrandish »

Liftyee wrote: post #65
Neywiny wrote: post #5

I actually like the 3.2 naming. Gen is speed, "by" is width. It puts it very roughly on par with PCIe's naming which nobody complains about. I just don't like that USB 3, USB 3.1, and USB 3.2 are the same things. And that sales people don't seem to understand that saying a chip supports 3.1 or 3.2 tells me it's anywhere from 5-20gbps which isn't ideal.

Out of curiosity, what do you use the higher 20gbps transfer speeds for? Video production? I use USB-C displays, but they run in DP Alt mode. I don't have many (any?) storage devices that can max out a 20gbps connection, and usually don't exceed 5gbps

> Out of curiosity, what do you use the higher 20gbps transfer speeds for?

Images, videos, movies, file transfer/backup. 50 megapixel RAW images from a DSLR that can capture up to 20 images a second get big. My daughter is a much better volleyball player than I am sports photographer, so I have to spray-and-pray to capture those high-speed hits at the net.

Transferring a few hundred such photos via a card reader was so glacially slow it was worth adding a 20Gbps USB3.2 2x2 port to my home server (Ryzen 5600x) via a dedicated PCI-E card. The USB3 ports on a good enthusiast-class mobo for that generation (only 4 yrs ago) max out at 5Gbps (theoretical). I would have added a 40Gbps Thunderbolt port instead but then I'd have to take a hit on the top speed of my second NVMe drive due to sharing PCI-E lanes.

While the increasing deployment of true USB4 ports is wonderful, it's not quite a panacea. Just because a port is labeled USB4 doesn't mean you necessarily get 40Gbps performance. USB bandwidth is shared across multiple ports via internal hubs and then the PCI-E lanes the hub is connected to might be shared with other peripherals (GFX, NVME, I/O cards). And different USB ports have different trade-offs depending on how they're internally connected, which isn't always documented well by mobo makers.

Sadly, in consumer systems the lack of PCI-E bandwidth can still be an issue if you want your expensive GPU to run maximally fast and have multiple fast NVMe drives. You have to spec your system carefully, get the latest generation hardware or pay 3-4x for HEDT/Enterprise chipset motherboards. Getting even 10s or 100s of gigs of data in or out of a PC reasonably quickly and conveniently has always been a bottleneck that's only getting somewhat better quite recently.

Re: USB Cheat Sheet (2022)

#88

Post by DHowett »

fabiensanglard wrote: post #83
DHowett wrote: post #10

Excellent article. If I could offer one correction, it would be that SBU (as specified by the USB 3.0 Promoter Group[1]) means "Sideband Use" rather than "Secondary Bus". On some devices, it is used to carry UART; on others, audio. [1]: https://www.usb.org/sites/default/files/USB%20Type-C%20Spec%... (pdf)

Thank you for taking the time to report the issue. It has now been addressed.

Oh wow, thank you!

Re: USB Cheat Sheet (2022)

#89

Post by crote »

adrian_b wrote: post #81
crote wrote: post #71

Earlier quoted context omitted.

It still would't be right. Full-featured USB-C has 8x superspeed (tx1p, tx1n, rx1p, rx1n, tx2p, tx2n, rx2p, rx2n), 2x high-speed (dp, dn), 2x power (vbus, gnd), 2x SBU, 1x CC. That's 15 wires.

A full-featured USB-C connector has 24 pins, as shown in a diagram in the parent article. The "12-wire" count of the parent article refers only to the main wires, i.e. the 4 USB 2.0 wires + 4 differential pairs for USB 3 or 4. Similarly, the "8-wire" count for Type A connectors refers only to the main wires, i.e. 4 USB 2.0 wires + 2 differential pairs for USB 3.

Yes, but not all of those 24 pins are used, and some of them are duplicated.

I also don't think you can make this "main wire" distinction: you shouldn't be counting the power wires if you only care about USB data in the Type A case, and you should arguably be counting the CC wire in the Type C case if you want to go for "strictly necessary to function", or the SBU wires if you want to go for "carries data at nontrivial speeds".

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